Web Admin 101

What is are buffer overflow attacks?

2008-11-21T12:32:00.000-08:00

Here is a very helpful article on Buffer Overflow Attacks and Their Countermeasures.

Great post on using SSH and SCP on irregular ports

2007-11-19T14:05:00.000-08:00

If you're trying to figure out how to use SSH on irregular ports, check out this article titled Correct syntax for using SSH and SFTP on Ubuntu on irregular ports.

I also found it useful for figuring out how to use the scp (secure copy) command between two different servers when root login is disabled.

Best article on Using tar to archive

2007-11-19T14:04:00.001-08:00

Found this article on Using tar to archive. Really good, step-by-step instructions.

Worthwhile, practical resource

2007-11-19T13:35:00.000-08:00

I just discovered the Seeksadmin blog, which has some fantastic articles on server security, including the following:

I'm looking forward to reading more gems from the Seeksadmin blog in the future.

CentOS Download Sites and Mirrors

2007-10-13T05:00:00.000-07:00

Download page on CentOS.org

Before downloading, the CentOS team would like to remind you that the primary means of sustaining the development of CentOS is via contributions by users such as yourself. CentOS is now and will continue to be totally free; however, it takes money and resources to make CentOS available. If you are able, please consider donating to the CentOS Project.

Specific download links for CentOS versions:

Awesome Linux Training Provider: SpiderTools.com

2007-10-12T19:44:00.000-07:00

An extremely exciting find: SpiderTools.com, which provides live online and asynchronous online/CD-ROM training courses on just what I need: basix Linux administration. This is perfect for daily 3 to 4 hour train commutes to work!

Books and CDs
Build a Computer on DVD for $12.95 dollars
Linux Newbie Book for $24.95
10 Point Security Check for $6.95

Asynchronous (Self-Paced) Courses
Basic Server Administration Workbook for $89.95
Linux Server Administration Six-Pack for $149.95

Synchronous (Live) Courses
Catalog of Real Training on Real Servers (Remote Access) from $149.00 to $1200.00

Introduction to Unix Commands

2007-10-12T16:09:00.000-07:00

Introduction to Unix commands from Indiana University Knowledge base

This is a very brief introduction to some useful Unix commands, including examples of how to use each command. For more extensive information about any of these commands, use the man command installed on your system.

Commands

`cal`	`cat`	`cd`	`chmod`
`cp`	`date`	`df`	`du`
`find`	`jobs`	`kill`	`less` and `more`
`lpr` and `lp`	`ls`	`man`	`mkdir`
`mv`	`ps`	`pwd`	`rm`
`rmdir`	`set`	`vi`	`w` and `who`

Sources for more information appear at the end of the online documentation.

CentOS-5 Online Documentation

2007-10-08T19:00:00.001-07:00

http://www.centos.org/docs/5/

CentOS.org - The Community ENTerprise Operating System

2007-10-08T18:59:00.001-07:00

http://www.centos.org/

General CentOS Questions

2007-10-08T18:57:00.000-07:00

http://www.centos.org/modules/smartfaq/category.php?categoryid=2

CLS (Clear Screen Command)

2007-10-07T21:02:00.000-07:00

From GRC | Security Now! Transcript #49:

Steve: For people who haven't used this command window a lot before, you want to know how to clear it in order to � from time to time, like before you issue a command, you might want to just get rid of all of the history that has scrolled by. The command for that is CLS. That's the clear screen command. So CLS, and then press Enter, will wipe that window clean and get ready for your next command.

netstat command (by Linux Network Administrators Guide)

2007-10-07T19:54:00.000-07:00

Chapter 5 of the Linux Network Administrators Guide offers a meaningful and well-organized outline on the ubiquitous netstat command. It is a 'must read' for anyone wishing to learn netstat. A brief overview of its contents:

5.9. The netstat Command
5.9.1. Displaying the Routing Table
5.9.2. Displaying Interface Statistics
5.9.3. Displaying Connections

Netstat command (Podcast)

2007-10-07T19:39:00.000-07:00

GRC Security Now! delivers podcasts on the topic of security through their weekly audio security column. The following link is a podcast on the netstat command:

Leo and I describe the operation and use of the universally available "Netstat" command -- available in every desktop operating system from Unix and Linux through Windows and Macs. "Netstat" allows anyone to instantly see what current Internet connections and listening ports any system has open and operating. Mastering the power of this little-known command will greatly empower any security-conscious computer user.

The website offers the content in various formats: higher and lower quality podcasts, supplementary notes, and a transcript in HTML, text only, or PDF format.

As of the date of this post, this is podcast #49 out of 112! This is an amazing website because each episode (like the one cited above) has six different resource formats:

High quality 64 kbps mp3 audio file
Quarter size, bandwidth-conserving, 16 kbps (lower quality) mp3 audio file
A web page with any supplementary notes
A web page text transcript of the episode
A simple text transcript of the episode
Ready-to-print PDF (Acrobat) transcript

(Note that the text transcripts will appear a few hours later than the audio files since they are created afterwards.)

You can subscribe to the ongoing series as an "RSS podcast" in order to have them automatically downloaded to you as they are produced. Alternatively, you can just get a simple email reminder.

Linux Network Administrators Guide

2007-10-07T19:36:00.000-07:00

The Table of Contents to the Linux Network Administrators Guide:

Preface

1. Purpose and Audience for This Book
2. Sources of Information
3. File System Standards
4. Standard Linux Base
5. About This Book
6. The Official Printed Version
7. Overview
8. Conventions Used in This Book
9. Submitting Changes
10. Acknowledgments

1. Introduction to Networking

1.1. History
1.2. TCP/IP Networks
1.3. UUCP Networks
1.4. Linux Networking
1.5. Maintaining Your System

2. Issues of TCP/IP Networking

2.1. Networking Interfaces
2.2. IP Addresses
2.3. Address Resolution
2.4. IP Routing
2.5. The Internet Control Message Protocol
2.6. Resolving Host Names

3. Configuringthe NetworkingHardware

3.1. Kernel Configuration
3.2. A Tour of Linux Network Devices
3.3. Ethernet Installation
3.4. The PLIP Driver
3.5. The PPP and SLIP Drivers
3.6. Other Network Types

4. Configuring the Serial Hardware

4.1. Communications Software for Modem Links
4.2. Introduction to Serial Devices
4.3. Accessing Serial Devices
4.4. Serial Hardware
4.5. Using the Configuration Utilities
4.6. Serial Devices and the login: Prompt

5. Configuring TCP/IP Networking

5.1. Mounting the /proc Filesystem
5.2. Installing the Binaries
5.3. Setting the Hostname
5.4. Assigning IP Addresses
5.5. Creating Subnets
5.6. Writing hosts and networks Files
5.7. Interface Configuration for IP
5.8. All About ifconfig
5.9. The netstat Command
5.10. Checking the ARP Tables

6. Name Service and Resolver Configuration

6.1. The Resolver Library
6.2. How DNS Works
6.3. Running named

7. Serial Line IP

7.1. General Requirements
7.2. SLIP Operation
7.3. Dealing with Private IP Networks
7.4. Using dip
7.5. Running in Server Mode

8. The Point-to-Point Protocol

8.1. PPP on Linux
8.2. Running pppd
8.3. Using Options Files
8.4. Using chat to Automate Dialing
8.5. IP Configuration Options
8.6. Link Control Options
8.7. General Security Considerations
8.8. Authentication with PPP
8.9. Debugging Your PPP Setup
8.10. More Advanced PPP Configurations

9. TCP/IP Firewall

9.1. Methods of Attack
9.2. What Is a Firewall?
9.3. What Is IP Filtering?
9.4. Setting Up Linux for Firewalling
9.5. Three Ways We Can Do Filtering
9.6. Original IP Firewall (2.0 Kernels)
9.7. IP Firewall Chains (2.2 Kernels)
9.8. Netfilter and IP Tables (2.4 Kernels)
9.9. TOS Bit Manipulation
9.10. Testing a Firewall Configuration
9.11. A Sample Firewall Configuration

10. IP Accounting

10.1. Configuring the Kernel for IP Accounting
10.2. Configuring IP Accounting
10.3. Using IP Accounting Results
10.4. Resetting the Counters
10.5. Flushing the Ruleset
10.6. Passive Collection of Accounting Data

11. IP Masquerade and Network Address Translation

11.1. Side Effects and Fringe Benefits
11.2. Configuring the Kernel for IP Masquerade
11.3. Configuring IP Masquerade
11.4. Handling Name Server Lookups
11.5. More About Network Address Translation

12. ImportantNetwork Features

12.1. The inetd Super Server
12.2. The tcpd Access Control Facility
12.3. The Services and Protocols Files
12.4. Remote Procedure Call
12.5. Configuring Remote Loginand Execution

13. The Network Information System

13.1. Getting Acquainted with NIS
13.2. NIS Versus NIS+
13.3. The Client Side of NIS
13.4. Running an NIS Server
13.5. NIS Server Security
13.6. Setting Up an NIS Client with GNU libc
13.7. Choosing the Right Maps
13.8. Using the passwd and group Maps
13.9. Using NIS with Shadow Support

14. The NetworkFile System

14.1. Preparing NFS
14.2. Mounting an NFS Volume
14.3. The NFS Daemons
14.4. The exports File
14.5. Kernel-Based NFSv2 Server Support
14.6. Kernel-Based NFSv3 Server Support

15. IPX and the NCP Filesystem

15.1. Xerox, Novell, and History
15.2. IPX and Linux
15.3. Configuring the Kernel for IPXand NCPFS
15.4. Configuring IPX Interfaces
15.5. Configuring an IPX Router
15.6. Mounting a Remote NetWare Volume
15.7. Exploring Some of the Other IPX Tools
15.8. Printing to a NetWare Print Queue
15.9. NetWare Server Emulation

16. ManagingTaylor UUCP

16.1. UUCP Transfers and Remote Execution
16.2. UUCP Configuration Files
16.3. Controlling Access to UUCP Features
16.4. Setting Up Your System for Dialing In
16.5. UUCP Low-Level Protocols
16.6. Troubleshooting
16.7. Log Files and Debugging

17. Electronic Mail

17.1. What Is a Mail Message?
17.2. How Is Mail Delivered?
17.3. Email Addresses
17.4. How Does Mail Routing Work?
17.5. Configuring elm

18. Sendmail

18.1. Introduction to sendmail
18.2. Installing sendmail
18.3. Overview of Configuration Files
18.4. The sendmail.cf and sendmail.mc Files
18.5. Generating the sendmail.cf File
18.6. Interpreting and Writing Rewrite Rules
18.7. Configuring sendmail Options
18.8. Some Useful sendmail Configurations
18.9. Testing Your Configuration
18.10. Running sendmail
18.11. Tips and Tricks

19. Getting EximUp and Running

19.1. Running Exim
19.2. If Your Mail Doesn't Get Through
19.3. Compiling Exim
19.4. Mail Delivery Modes
19.5. Miscellaneous config Options
19.6. Message Routing and Delivery
19.7. Protecting Against Mail Spam
19.8. UUCP Setup

20. Netnews

20.1. Usenet History
20.2. What Is Usenet, Anyway?
20.3. How Does Usenet Handle News?

21. C News

21.1. Delivering News
21.2. Installation
21.3. The sys File
21.4. The active File
21.5. Article Batching
21.6. Expiring News
21.7. Miscellaneous Files
21.8. Control Messages
21.9. C News in an NFS Environment
21.10. Maintenance Tools and Tasks

22. NNTP and thenntpd Daemon

22.1. The NNTP Protocol
22.2. Installing the NNTP Server
22.3. Restricting NNTP Access
22.4. NNTP Authorization
22.5. nntpd Interaction with C News

23. Internet News

23.1. Some INN Internals
23.2. Newsreaders and INN
23.3. Installing INN
23.4. Configuring INN: the Basic Setup
23.5. INN Configuration Files
23.6. Running INN
23.7. Managing INN: The ctlinnd Command

24. Newsreader Configuration

24.1. tin Configuration
24.2. trn Configuration
24.3. nn Configuration

A. Example Network:The Virtual Brewery

A.1. Connecting the Virtual Subsidiary Network

B. Useful Cable Configurations

B.1. A PLIP Parallel Cable
B.2. A Serial NULL Modem Cable

C. Linux Network Administrator's Guide, Second Edition Copyright Information

C.1. 0. Preamble
C.2. 1. Applicability and Definitions
C.3. 2. Verbatim Copying
C.4. 3. Copying in Quantity
C.5. 4. Modifications
C.6. 5. Combining Documents
C.7. 6. Collections of Documents
C.8. 7. Aggregation with Independent Works
C.9. 8. Translation
C.10. 9. Termination
C.11. 10. Future Revisions of this License

D. SAGE: The SystemAdministrators Guild

Index

List of Tables
2-1. IP Address Ranges Reserved for Private Use
4-1. setserial Command-Line Parameters
4-2. stty Flags Most Relevant to Configuring Serial Devices
7-1. Linux Slip-Line Disciplines
7-2. /etc/diphosts Field Description
9-1. Common Netmask Bit Values
9-2. ICMP Datagram Types
9-3. Suggested Uses for TOS Bitmasks
13-1. Some Standard NIS Maps and Corresponding Files
15-1. XNS, Novell, and TCP/IP Protocol Relationships
15-2. ncpmount Command Arguments
15-3. Linux Bindery Manipulation Tools
15-4. nprint Command-Line Options

List of Figures
1-1. The three steps of sending a datagram from erdos to quark
2-1. Subnetting a class B network
2-2. A part of the net topology at Groucho Marx University
3-1. The relationship between drivers, interfaces, and hardware
6-1. A part of the domain namespace
9-1. The two major classes of firewall design
9-2. The stages of IP datagram processing
9-3. FTP server modes
9-4. A simple IP chain ruleset
9-5. The sequence of rules tested for a received UDP datagram
9-6. The rules flow for a received TCP datagram for ssh
9-7. The rules flow for a received TCP datagram for telnet
9-8. Datagram processing chain in IP chains
9-9. Datagram processing chain in netfilter
11-1. A typical IP masquerade configuration
15-1. IPX internal network
16-1. Interaction of Taylor UUCP configuration files
20-1. Usenet newsflow through Groucho Marx University
21-1. News flow through relaynews
23-1. INN architecture (simplified for clarity)
A-1. The Virtual Brewery and Virtual Winery subnets
A-2. The Virtual Brewery Network
B-1. Parallel PLIP cable
B-2. Serial NULL-Modem cable

List of Examples
4-1. Example rc.serial setserial Commands
4-2. Output of setserial -bg /dev/ttyS Command
4-3. Example rc.serial stty Commands
4-4. Example rc.serial stty Commands Using Modern Syntax
4-5. Output of stty -a Command
4-6. Sample /etc/mgetty/mgetty.config File
6-1. Sample host.conf File
6-2. Sample nsswitch.conf File
6-3. Sample nsswitch.conf File Using an Action Statement
6-4. An Excerpt from the named.hosts File for the Physics Department
6-5. An Excerpt from the named.hosts File for GMU
6-6. An Excerpt from the named.rev File for Subnet 12
6-7. An Excerpt from the named.rev File for Network 149.76
6-8. The named.boot File for vlager
6-9. The BIND 8 equivalent named.conf File for vlager
6-10. The named.ca File
6-11. The named.hosts File
6-12. The named.local File
6-13. The named.rev File
7-1. A Sample dip Script
12-1. A Sample /etc/inetd.conf File
12-2. A Sample /etc/services File
12-3. A Sample /etc/protocols File
12-4. A Sample /etc/rpc File
12-5. Example ssh Client Configuration File
13-1. Sample ypserv.securenets File
13-2. Sample nsswitch.conf File
18-1. Sample Configuration File vstout.smtp.m4
18-2. Sample Configuration File vstout.uucpsmtp.m4
18-3. Rewrite Rule from vstout.uucpsmtp.m4
18-4. Sample aliases File
18-5. Sample Output of the mailstats Command
18-6. Sample Output of the oststat Command

This Guide is one of numerous online publications by Internet FAQ Archives.

10 Commands Every Linux Developer Should Know

2007-10-06T22:26:00.001-07:00

http://www.linuxjournal.com/article/7330

netstat

2007-10-06T22:22:00.000-07:00

http://www.itwire.com/index2.php?option=com_content&do_pdf=1&id=13758
http://www.leadershipbynumbers.com/MS.nsf/d6plinks/BMMA-66RP4U
http://www.linuxkp.org/en/content.php?&content/server/fire3.html#netstat

Securing Linux in a Nutshell

2007-10-06T22:16:00.000-07:00

http://uhacc.org/tech_docs/guides/secure_linux.php

Beginner's Guide to Firewalls

2007-10-06T22:14:00.000-07:00

http://www.jmu.edu/computing/security/info/pfw.shtml

Brain dump of more Best Linux Resources

2007-10-05T17:35:00.000-07:00

http://www.fsf.org/
http://www.kernel.org/
http://www.opensource.org
http://www.osdl.org/
http://www.sourceforge.net/
http://www.slashdot.org/
http://www.gpl-violations.org/
http://www.vmware.com/
"Preventing Web Attacks with Apache" (2006) Ryan C. Barnett. ISBN 0-321-32128-6

MySQL Forums by MySQL AB

2007-09-26T15:19:00.000-07:00

From MySQL 5.0 Reference Manual by MySQL AB:

If you have questions about using MySQL, you can ask them using our mailing lists or forums. See Section 1.7.1, “MySQL Mailing Lists”, and Section 1.7.2, “MySQL Community Support at the MySQL Forums”. If you have suggestions concerning additions or corrections to the manual itself, please send them to the documentation team at <docs@mysql.com>.

MySQL 5.0 and 5.1 Reference Manuals

2007-09-26T14:55:00.000-07:00

MySQL AB is the company that created the MySQL database system. It's reference manuals are a cornerstone of any definitive library of MySQL:

The MySQL 5.0 Reference Manual

The following list describes some sections of particular interest in this manual:

For a discussion about the capabilities of the MySQL Database Server, see Section 1.4.3, “The Main Features of MySQL”.
For future plans, see Section 1.6, “MySQL Development Roadmap”.
For installation instructions, see Chapter 2, Installing and Upgrading MySQL. For information about upgrading MySQL, see Section 2.4.17, “Upgrading MySQL”.
For a tutorial introduction to the MySQL Database Server, see Chapter 3, Tutorial.
For information about configuring and administering MySQL Server, see Chapter 5, Database Administration.
For information about setting up replication servers, see Chapter 15, Replication.
For answers to a number of questions that are often asked concerning the MySQL Database Server and its capabilities, see Appendix A, MySQL 5.0 Frequently Asked Questions.
For a list of currently known bugs and misfeatures, see Section B.1.8, “Known Issues in MySQL”.
For a list of all the contributors to this project, see Appendix G, Credits.
For a history of new features and bugfixes, see Appendix E, MySQL Change History.
For tips on porting the MySQL Database Software to new architectures or operating systems, see MySQL Internals: Porting.
For benchmarking information, see the sql-bench benchmarking directory in your MySQL distribution.

The MySQL 5.1 Reference Manual

Database Journal: MySQL

2007-09-26T14:49:00.000-07:00

Database Journal is one of the best resources on all major database systems including a section devoted to MySQL. A sampling of articles from September 2007:

Introduction to Relational Databases

2007-09-26T04:04:00.000-07:00

From Introduction to Relational Databases by Ian Gilfillan:

Many web developers are self-taught, learning HTML, then moving on to a programming language such as PHP. From there, they often learn to integrate this with a database. Too few though have a good theoretical knowledge of databases. Mention foreign keys, or referential integrity, and you're met with a blank stare. Small databases can be easily designed with little database theory knowledge. But large databases can easily get out of hand when badly designed, leading to poor performance, and resulting in the whole database needing to be rebuilt later. This article is a brief introduction to the topic of relational databases, and will hopefully whet your appetite for further exploration...

MDLog:/sysadmin - The Journal of a Linux Sysadmin

2007-09-23T10:11:00.000-07:00

MDLog:/sysadmin - The Journal of a Linux Sysadmin:

My name is Marius Ducea. I’m living in Romania, in a city called Sibiu, with my
beautiful wife, Anca, which still has the patience to put up with the long hours
I spend in front of the computer.
I have been working as a System
Administrator (sysadmin) for my entire career (about 7 years). I used to work in
various local companies all in the ISP field in positions like system
administrator, network administrator, security specialist, technical manager.
About 2 years ago I have started my own consulting company, and started
freelancing and working on various contract projects. I have ended doing this as
a full time job now and I ended up focusing on my own business than working for
someone else.
Some of the certifications I have earned until now:
Cisco
Certified Network Associate (CCNA)
Cisco Certified Network Professional
(CCNP)
Brainbench.com, UNIX System Administrator (Job
Role)
Brainbench.com, Linux System Administrator
(Job Role)
Brainbench.com, Windows System Administrator
(Job Role)
Brainbench.com, Network Support Specialist
(Job Role)
Brainbench.com, Information Security
Administrator (Job Role)
Brainbench.com, Network Administrator (Job
Role)
Brainbench.com, Web Administrator (BCIP)
www.ducea.com is my own online journal, where I
will share my experience about managing and maintaining Linux servers. You will
find here articles about sysadmin tasks, mostly about Linux, from things I have
done, challenges I have passed, that hopefully will be useful to other peoples
like you also.If you would like me to write about something particular, or you
have any suggestion for this site, please use the contact form.

Checking and Setting Time on Linux Servers

2007-09-23T06:49:00.000-07:00

How To Set the Time Zone? On modern linux systems the easiest way to get the correct time on your OS is to use ntp...

Daylight Saving Time (DST) Handling in Linux? The Linux kernel maintains a system time. This time is initialized at boot time using the hardware clock (also known as real time clock, RTC, BIOS clock or CMOS clock). As the hardware clock does not provide not information as to whether it is kept in UTC or in local time, this needs to be configured explicitly, in YaST -> System -> /etc/sysconfig Editor -> System -> Environment -> Clock -> HWCLOCK. ...

Linux Tips: Linux, Clocks, and Time. This document explains how to set your computer's clock from Linux, how to set your timezone, and other stuff related to Linux and how it does its time-keeping. Your computer has two timepieces; a battery-backed one that is always running (the ``hardware'', ``BIOS'', or ``CMOS'' clock), and another that is maintained by the operating system currently running on your computer (the ``system'' clock). The hardware clock is generally only used to set the system clock when your operating system boots, and then from that point until you reboot or turn off your system, the system clock is the one used to keep track of time.

What do some common Unix file extensions mean?

2007-09-15T09:56:00.000-07:00

In Unix, how do I list the files in a directory?From the Indiana University UITS Knowledgebase, common Unix file extensions include:

.asc - ASCII (text) file, often containing ANSI codes
.awk - awk script
.bak - Backup copy of file
.bz2 - bzip2 compressed file
.c - C program source code
.C - C++ program source code
.cc - C++ program source code
.cgi - CGI web page program
.dat - Data or other information
.doc - Explanatory text file
.dvi - DVI format document, produced by TeX/LaTeX
.el - Emacs Lisp source code
.elc - Compiled Emacs Lisp program
.f - Fortran source code
.f77 - Fortran source code (f77 compiler)
.fig - Xfig data file
.for - Fortran source code (fort compiler)
.gif - GIF image file
.gz - gzip compressed file
.h - C or C++ program header file
.html - Hypertext Markup Language document
.info - Emacs TeXinfo file in "info" format
.jpg - Graphical image file in JPEG format
.log - Logged information
.m - Maple file
.mat - Matlab script
.me - nroff input file for processing with -me option
.mpg - MPEG animation file
.ms - nroff input file for processing with -ms option
.o - Object code, produced by compilers
.pal - Xpaint palette file
.pbm - Portable bitmap
.pgm - Portable gray scale pixmap
.pl - Perl program
.png - PNG format graphics file (similar to GIF)
.ppm - Portable pixmap
.ps - PostScript format document
.py - Python program
.rast - Sun raster file
.rgb - SGI native image file
.shar - Shell archive (expand with sh file.shar)
.ss - Scheme source code
.S - Assembly (machine) code
.tar - Tape archive, used by tar command
.tar.gz - Tarred-then-gzipped files
.tex - TeX or LaTeX format document
.tif - TIFF (Adobe) image file
.tgz - Tarred-then-gzipped files (equivalent to .tar.gz)
.txt - Generic text file
.uue - uuencoded file
.xbm - X bitmap
.z - Packed file (from the pack command) or early gzip file
.Z - Compressed file, from compress command
.zip - Zipped (compressed) file, from zip command

Some others include:

*~ …(File ending with ~ ) Emacs backup file
#*# …(File surrounded with #'s) Emacs autobackup file
,* …(File beginning with , ) MH removed message
.*rc …(File starting with a dot, ending with rc) configuration file

Lastly, files with an extension that is a number or a number plus a letter (e.g., cat.1, dbm.3b) are often manual page files, in runoff format.

In Unix, how do I list the files in a directory? ls

2007-09-15T09:54:00.000-07:00

In Unix, how do I list the files in a directory? From the Indiana University UITS Knowledbase:

You can use the ls command to list the files in any directory to which you have access. For a simple directory listing, at the Unix prompt, enter:

ls

The options available with ls are far too numerous to list here, but you can see them all in the online manual (man) pages by entering man ls at the Unix prompt. Some of the more common options, however, include:

You can limit the files that are described by using fragments of filenames and * ? wildcards. The * represents any number of unknown characters, while ? represents only one unknown character. You can use * and ? anywhere in the filename fragment.
If you would like to list files in another directory, use the ls command along with the path to the directory. For example, if you are in your home directory and want to list the contents of the /etc directory, enter: ls /etc. This will list the contents of the /etc directory in columns.
Several options control the way in which the information you get is displayed. Options are used in this format: ls -option filename. Neither the options nor the filename are required (you may use ls by itself to see all the files in a directory). You may have multiple options and multiple filenames on a line.
Some of the more helpful options for ls are:
-a which shows all files, including those beginning with . (a period). The dot is special in the Unix file system.
-d which shows directory names, but not contents.
-F which marks special files with symbols to indicate what they are: / for directories, @ for symbolic links, * for executable programs.
-l which shows the rights to the file, the owner, the size in bytes, and the time of the last modification made to the file. (The l stands for "long".)
-R which recursively lists subdirectories.
The options can be combined. To list all the files in a directory in the long format, with marks for the types of files, you would enter: ls -Flg
As with many other Unix commands, you can redirect the output from ls to a file, or pipe it to another command.
If you want to save a list of the files in your directory to a file named foo, you would use the following command combination: ls > foo
If you want to mail a list of the files in your directory to a user named tony, you would use the following combination: ls Mail tony

To see the files beginning with a dot in your home directory, enter at the Unix prompt:
ls -ad ~/.*For example, many rc files have a filename that begins with a . (dot), which means that you normally won't see them when you use the just the "ls" command.

Also see:
In Unix, how do I get a recursive directory listing?
In Unix, how do I remove a directory?
In Unix, how do I create a new directory?
In Unix, what is the find command, and how do I use it to search through directories for files?
What do some common Unix file extensions mean?
In Unix, what command can I use other than "ls" or "ls -l" to list the files in a directory?

In Unix, what do some obscurely named commands stand for?

2007-09-15T09:38:00.000-07:00

A list of some of the more obscurely named Unix commands follows from the Indiana University UITS Knowledbase:

awk - Aho, Weinberger, Kernighan - how do I use awk?
grep - Global regular expression point - how do I use grep?
fgrep - Fixed grep
egrep - Extended grep
cat - Catenate - In Unix, how do I combine several files into a single file?
nroff - New roff
troff - Typsetter new roff
tee - T
biff - A dog named Biff
rc - runcom
Perl - Practical extraction and reporting language - more info

Click on the link to for basic definitions of the acronyms/terms listed above.

What does Unix stand for?

2007-09-15T09:33:00.001-07:00

What does Unix stand for? From Indiana University UITS Knowledgebase:

Unix is not an acronym; it is a pun on "Multics". Multics is a large multi-user operating system that was being developed at Bell Labs shortly before Unix was created in the early '70s. Brian Kernighan is credited with the name.

27 Things You Don't Know about PHP

2007-09-14T18:59:00.000-07:00

27 Things You Don't Know about PHP:

12 Things You Should Dislike About PHP

Another impressive list of things you may not know about PHP, this time focusing on the annoying foibles of the language.

(tags: php )

15 Cool Things About PHP That Most People Overlook

Far from another lame collection of semi-obscure PHP functions, this list of language features will likely contain at least a few mind-blowing items for all but the most seasoned of PHP veterans.

(tags: php )

What is a Hypervisor?

2007-09-14T15:33:00.001-07:00

What is Bare Metal?

2007-09-14T15:32:00.000-07:00

VMware and Virtualization

2007-09-14T15:26:00.000-07:00

Dear Customer,

You're about to find out how using VMware and Intel to virtualize
can give you reliability, value and ease of deployment.

In addition to the virtualization kit, you may also learn more by taking
advantage of many available resources.

TCO Calculator
This new online tool is designed to provide a total cost of
ownership analysis in minutes by comparing your current
environment to a virtualized VMware environment.

Intel Virtualization Resource Center
Learn more about the performance benefits provided by virtualizing
on Quad-Core Intel(R) Xeon(R) processors.

Webinars
View live and on-demand webinars discussing various VMware
product, customer, and partner topics.

Additionally, get the latest information on:
Data Center Solutions
Desktop Solutions
Business Continuity Solutions

We look forward to a continued relationship.

Best regards,
The VMware and Intel Teams

VMware, Inc. 3401 Hillview Ave Palo Alto CA 94304 USA Tel 1-877-486-9273 Copyright © 2007 VMware, Inc. All rights reserved. VMware is a registered trademark of VMware, Inc.

Thank you for registering with VMware. Any information that you provide to VMware will be treated in accordance with our Privacy Policy.

To manage your VMware subscription, please visit VMware Subscriptions.

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Intel Corporation in the U.S. and other countries.
Legal Information

Database Corrupted? mysqlcheck vs myisamchk

2007-09-13T13:24:00.000-07:00

From Repairing Database Corruption in MySQL by Ian Gilfillan:

There are three ways to check tables. All of these work with MyISAM tables, the default, non-transactional table type, and one with InnoDB, the most mature of the MySQL transactional table types. Fortunately, MySQL now allows you to check tables while the server is still running, so corruption in a minor table need not affect everything on the server.

The CHECK TABLE SQL statement (obviously the server must be running for this)
Running the mysqlcheck command-line utility (the server can be running)
Running the myisamchk command-line utility (the server must be down, or the tables inactive)

From O'Reilly MySQL Certification Study Guide:

Checking Tables with mysqlcheck and myisamchk
The mysqlcheck and myisamchk programs are used to check and repair tables (primarily MyISAM tables). They can help you keep your tables free from problems, or repair them if problems do occur—for example, if a MyISAM table becomes damaged as the result of a server crash.
mysqlcheck and myisamchk are similar in purpose, but they do have some differences. Here's a comparison of the two programs:

From mysqlcheck — A Table Maintenance and Repair Program by MySQL AB:

The mysqlcheck client checks, repairs, optimizes, and analyzes tables.

mysqlcheck is similar in function to myisamchk, but works differently. The main operational difference is that mysqlcheck must be used when the mysqld server is running, whereas myisamchk should be used when it is not. The benefit of using mysqlcheck is that you do not have to stop the server to check or repair your tables.

mysqlcheck uses the SQL statements CHECK TABLE, REPAIR TABLE, ANALYZE TABLE, and OPTIMIZE TABLE in a convenient way for the user. It determines which statements to use for the operation you want to perform, and then sends the statements to the server to be executed. For details about which storage engines each statement works with, see the descriptions for those statements in Chapter 12, SQL Statement Syntax.
The MyISAM storage engine supports all four statements, so mysqlcheck can be used to perform all four operations on MyISAM tables. Other storage engines do not necessarily support all operations. In such cases, an error message is displayed.

Unix Basics from IU Knowledgebase

2007-09-12T14:05:00.000-07:00

Unix Basics:

The following is a small selection of introductory texts from Indiana University's Knowledge Base. You can also search for particular words or phrases throughout the entire Knowledge Base with the full-text search.

Contents

Indiana University Technical Knowledgebase

2007-09-12T13:29:00.000-07:00

Menus of The Indiana University Technical Knowledge Base

These menus organize only a small selection of the Knowledge Base, with links to about 1,400 introductory documents. Select a topic from the menu below to see questions and answers on that topic. To access all information in the Knowledge Base (over 13,000 documents), use the full-text search. For help with using the menus, see Help with the KB menu interface.

For additional help, see the UITS Services and Support Training and Workshops section.

What are cron and crontab, and how do I use them?

2007-09-12T11:52:00.000-07:00

What are cron and crontab, and how do I use them?

For commands that need to be executed repeatedly (e.g., hourly, daily, or weekly), you can use the crontab command. The crontab command creates a crontab file containing commands and instructions for the cron daemon to execute. You can use the crontab command with the following options:

crontab -a filename
Install filename as your crontab file. On many systems,
this command is executed simply as crontab filename (i.e., without the
-a option).
crontab -e
Edit your crontab file, or create one
if it doesn't already exist.
crontab -l
Display your crontab file.
crontab -r
Remove your crontab file.
crontab -v
Display the last
time you edited your crontab file. (This option is available on only a few
systems.)
crontab -u user
Used in conjunction with other options, this
option allows you to modify or view the crontab file of user. When available,
only administrators can use this option.

Each entry in a crontab file consists of six fields, specifying in the following order:

minute(s) hour(s) day(s) month(s) weekday(s) command(s)

MySQL migration: MyISAM to InnoDB

2007-09-11T20:42:00.001-07:00

http://www.linux.com/articles/46370

MySQL Documentation by MySQL AB

2007-09-11T20:41:00.001-07:00

http://dev.mysql.com/doc/#manual

UNIX Administration Course (1999)

2007-09-11T20:27:00.000-07:00

http://www.futuretech.blinkenlights.nl/admin/day2d.html

HTML Help FAQ

2007-09-10T23:31:00.000-07:00

HTML Help FAQ by the Web Design Group:

Full Table of Contents

HTML - Special Entity Codes

2007-09-10T23:29:00.000-07:00

HTML - Special Entity Codes:

Letters with Accents - (e.g. ó, ò, ñ)
- Expanded Accents Listing (Unicode) - Phonetics Information Page
Other Foreign Characters - (e.g. ç, ¿, ß)
- Expanded Foreign Characters (Unicode) - Phonetics Information Page
Currency Symbols - (e.g. ¢, £, ¥)
Math Symbols - (e.g. ±, °, ÷)
Using the Codes
Uniciode Numeric Codes - New Page
Links to Other References

Understanding the outputs of Top Command

2007-09-10T07:53:00.000-07:00

The Top Command

2007-09-09T08:54:00.000-07:00

from About.com:

NAMEtop - display top CPU processes
SYNOPSIStop [-] [d
delay] [p pid] [q] [c] [C] [S] [s] [i] [n iter] [b]
DESCRIPTIONtop provides an ongoing look at processor activity
in real time. It displays a listing of the most CPU-intensive tasks on the
system, and can provide an interactive interface for manipulating processes. It
can sort the tasks by CPU usage, memory usage and runtime. can be better
configured than the standard top from the procps suite. Most features can either
be selected by an interactive command or by specifying the feature in the
personal or system-wide configuration file. See below for more information.

COMMAND-LINE OPTIONSd Specifies the delay between
screen updates. You can change this with the s interactive command. p Monitor
only processes with given process id. This flag can be given up to twenty times.
This option is neither available interactively nor can it be put into the
configuration file. q This causes top to refresh without any delay. If the
caller has superuser privileges, top runs with the highest possible priority. S
Specifies cumulative mode, where each process is listed with the CPU time that
it as well as its dead children has spent. This is like the -S flag to ps(1). See the
discussion below of the S interactive command. s Tells top to run in secure
mode. This disables the potentially dangerous of the interactive commands (see
below). A secure top is a nifty thing to leave running on a spare terminal. i
Start top ignoring any idle or zombie processes. See the interactive command i
below. C display total CPU states instead of individual CPUs. This option only
affects SMP systems. c display command line instead of the command name only.
The default behavior has been changed as this seems to be more useful. H Show
all threads. n Number of iterations. Update the display this number of times and
then exit. b Batch mode. Useful for sending output from top to other programs or
to a file. In this mode, top will not accept command line input. It runs until
it produces the number of iterations requested with the n option or until
killed. Output is plain text suitable for display on a dumb terminal.
FIELD DESCRIPTIONStop displays a variety of information about
the processor state. The display is updated every 5 seconds by default, but you
can change that with the d command-line option or the s interactive command.
"uptime" This line displays the time the system has been up, and the three load
averages for the system. The load averages are the average number of process
ready to run during the last 1, 5 and 15 minutes. This line is just like the
output of uptime(1). The
uptime display may be toggled by the interactive l command. processes The total
number of processes running at the time of the last update. This is also broken
down into the number of tasks which are running, sleeping, stopped, or undead.
The processes and states display may be toggled by the t interactive command.
"CPU states" Shows the percentage of CPU time in user mode, system mode, niced
tasks, iowait and idle. (Niced tasks are only those whose nice value is
positive.) Time spent in niced tasks will also be counted in system and user
time, so the total will be more than 100%. The processes and states display may
be toggled by the t interactive command. Mem Statistics on memory usage,
including total available memory, free memory, used memory, shared memory, and
memory used for buffers. The display of memory information may be toggled by the
m interactive command. Swap Statistics on swap space, including total swap
space, available swap space, and used swap space. This and Mem are just like the
output of free(1). PID The
process ID of each task. PPID The parent process ID each task. UID The user ID
of the task's owner. USER The user name of the task's owner. PRI The priority of
the task. NI The nice value of the task. Negative nice values are higher
priority. SIZE The size of the task's code plus data plus stack space, in
kilobytes, is shown here. TSIZE The code size of the task. This gives strange
values for kernel processes and is broken for ELF processes. DSIZE Data + Stack
size. This is broken for ELF processes. TRS Text resident size. SWAP Size of the
swapped out part of the task. D Size of pages marked dirty. LC Last used
processor. (That this changes from time to time is not a bug; Linux
intentionally uses weak affinity. Also notice that the very act of running top
may break weak affinity and cause more processes to change current CPU more
often because of the extra demand for CPU time.) RSS The total amount of
physical memory used by the task, in kilobytes, is shown here. For ELF processes
used library pages are counted here, for a.out processes not. SHARE The amount
of shared memory used by the task is shown in this column. STAT The state of the
task is shown here. The state is either S for sleeping, D for uninterruptible
sleep, R for running, Z for zombies, or T for stopped or traced. These states
are modified by trailing < for a process with negative nice value, N for a
process with positive nice value, W for a swapped out process (this does not
work correctly for kernel processes). WCHAN depending on the availability of
either /boot/psdatabase or the kernel link map /boot/System.map this shows the
address or the name of the kernel function the task currently is sleeping in.
TIME Total CPU time the task has used since it started. If cumulative mode is
on, this also includes the CPU time used by the process's children which have
died. You can set cumulative mode with the S command line option or toggle it
with the interactive command S. The header line will then be changed to CTIME.
%CPU The task's share of the CPU time since the last screen update, expressed as
a percentage of total CPU time per processor. %MEM The task's share of the
physical memory. COMMAND The task's command name, which will be truncated if it
is too long to be displayed on one line. Tasks in memory will have a full
command line, but swapped-out tasks will only have the name of the program in
parentheses (for example, "(getty)"). "A , WP" these fields from the kmem top
are not supported.
INTERACTIVE COMMANDSSeveral single-key
commands are recognized while top is running. Some are disabled if the s option
has been given on the command line. space Immediately updates the display. ^L
Erases and redraws the screen. "h or ?" Displays a help screen giving a brief
summary of commands, and the status of secure and cumulative modes. k Kill a
process. You will be prompted for the PID of the task, and the signal to send to
it. For a normal kill, send signal 15. For a sure, but rather abrupt, kill, send
signal 9. The default signal, as with kill(1), is 15,
SIGTERM. This command is not available in secure mode. i Ignore idle and zombie
processes. This is a toggle switch. I Toggle between Solaris (CPU percentage
divided by total number of CPUs) and Irix (CPU percentage calculated solely by
amount of time) views. This is a toggle switch that affects only SMP systems. "n
or #" Change the number of processes to show. You will be prompted to enter the
number. This overrides automatic determination of the number of processes to
show, which is based on window size measurement. If 0 is specified, then top
will show as many processes as will fit on the screen; this is the default. q
Quit. r Re-nice a process. You will be prompted for the PID of the task, and the
value to nice it to. Entering a positve value will cause a process to be niced
to negative values, and lose priority. If root is running top, a negative value
can be entered, causing a process to get a higher than normal priority. The
default renice value is 10. This command is not available in secure mode. S This
toggles cumulative mode, the equivalent of ps -S, i.e., that CPU times will
include a process's defunct children. For some programs, such as compilers,
which work by forking into many separate tasks, normal mode will make them
appear less demanding than they actually are. For others, however, such as
shells and init, this behavior is correct. In any case, try cumulative mode for
an alternative view of CPU use. s Change the delay between updates. You will be
prompted to enter the delay time, in seconds, between updates. Fractional values
are recognized down to microseconds. Entering 0 causes continuous updates. The
default value is 5 seconds. Note that low values cause nearly unreadably fast
displays, and greatly raise the load. This command is not available in secure
mode. "f or F" Add fields to display or remove fields from the display. See
below for more information. "o or O" Change order of displayed fields. See below
for more information. l toggle display of load average and uptime information. m
toggle display of memory information. t toggle display of processes and CPU
states information. c toggle display of command name or full command line. N
sort tasks by pid (numerically). A sort tasks by age (newest first). P sort
tasks by CPU usage (default). M sort tasks by resident memory usage. T sort
tasks by time / cumulative time. W Write current setup to ~/.toprc. This is the
recommended way to write a top configuration file.
The
Field and Order ScreensAfter pressing f, F, o or O you will be shown a screen
specifying the field order on the top line and short descriptions of the field
contents. The field order string uses the following syntax: If the letter in the
filed string corresponding to a field is upper case, the field will be
displayed. This is furthermore indicated by an asterisk in front of the field
description. The order of the fields corresponds to the order of the letters in
the string. From the field select screen you can toggle the display of a field
by pressing the corresponding letter. From the order screen you may move a field
to the left by pressing the corresponding upper case letter resp. to the right
by pressing the lower case one.
Configuration FilesTop
reads it's default configuration from two files, /etc/toprc and ~/.toprc. The
global configuration file may be used to restrict the usage of top to the secure
mode for non-non-privileged users. If this is desired, the file should contain a
's' to specify secure mode and a digit d (2<=d<=9) for the default delay
(in seconds) on a single line. The personal configuration file contains two
lines. The first line contains lower and upper letters to specify which fields
in what order are to be displayed. The letters correspond to the letters in the
Fields or Order screens from top. As this is not very instructive, it is
recommended to select fields and order in a running top process and to save this
using the W interactive command. The second line is more interesting (and
important). It contains information on the other options. Most important, if you
have saved a configuration in secure mode, you will not get an insecure top
without removing the lower 's' from the second line of your ~/.toprc. A digit
specifies the delay time between updates, a capital 'S' cumulative mode, a lower
'i' no-idle mode, a capital 'I' Irix view. As in interactive mode, a lower 'm',
'l', and 't' suppresses the display of memory, uptime resp. process and CPU
state information. Currently changing the default sorting order (by CPU usage)
is not supported.
SEE ALSOps(1), free(1), uptime(1), kill(1), renice(1).
Important: Use the man command (% man) to see how a command is
used on your particular computer.

Top 10 Tips for Linux Users

2007-09-09T07:43:00.000-07:00

Top 10 Tips for Linux Users:

Everyone develops their favorite tips and tricks for using Linux based on their
own experience and the kind of work they are doing. Here are some of mine. These
tips may seem simple, but I've found it's often the simple tricks that are the
most useful in day-to-day work.

1. Switch to another console.
Linux lets you use "virtual consoles" to log on to multiple sessions
simultaneously, so you can do more than one operation or log on as another user.
Logging on to another virtual console is like sitting down and logging in at a
different physical terminal, except you are actually at one terminal, switching
between login sessions.
Virtual consoles are especially useful if you aren't
running X, but you can use them even if you are.

In early versions
of the kernel (pre-1.1.54), the number of available virtual consoles was
compiled into the kernel. With more recent kernels, 63 virtual consoles are
available, with 6 set up by default in the file /etc/inittab.

Use
the key combination Alt+Fn to switch between virtual consoles, where Fn is one
of the function keys F1-F6. (If you are in X, you'll probably need to use
Ctrl-Alt-Fn instead.) Alt+F7 gets you back to your X session, if one is running.
You can rotate between consoles with the Alt-right arrow and Alt-left arrow key
combinations.

2. Temporarily use a different shell. Every user
account has a shell associated with it. The default Linux shell is bash; a
popular alternative is tcsh. The last field of the password table (/etc/passwd)
entry for an account contains the login shell information. You can get the
information by checking the password table, or you can use the finger command.
For example, the command "finger ellen" shows, among other things, that I use
/bin/tcsh.

The command chsh changes the login shell for all future
logins; that is, it changes the account entry in the password table to reflect
the new shell. However, you can also temporarily use another shell at any time
by simply running the new shell. For example, if I want to try something out in
bash, I can type "bash" at the prompt and be put into a bash shell. Typing
either Ctrl-d or exit gets rid of that shell and returns me to my tcsh
session.

3. Print a man page. Here are a few useful tips for
viewing or printing manpages:
To print a manpage, run the command:

man col -b lpr

The col -b
command removes any backspace or other characters that would make the printed
manpage difficult to read.

Also, if you want to print a manpage
that isn't in a standard man directory (i.e., it's in a directory that isn't
specified in the MANPATH environment variable), you can specify the full
pathname of the manpage, including the full filename:

man
/work/myapp/mymanpage.1

If you use the Emacs editor, you can view
a manpage with the command Meta-x man; Emacs then prompts you for the name of
the manpage. You can view the page or print it as you would any other Emacs
buffer.

As a last resort, you can format the manpage directly with
the groff command. However, the default output is a PostScript file, so you'll
want to either send it to a PostScript printer or to a viewer such as ghostview:

groff -man /work/myapp/mymanpage.1 ghostview -i

You can get ASCII output with the -a option, but the result is
unformatted text. Not pretty to read, but it might suffice if nothing else
works.

4. Use command substitution to simplify complex operations.
Command substitution lets you use the output of one command as an input argument
to another command. To use command substitution, determine what command will
generate the output you want, put that command in backquotes, and use it as an
argument to another command. For example, I often use command substitution to
recursively grep the files in a directory tree:
grep 'Title' `find /work
-type f -name 'chap*' -print` > chaptitles

The portion of this
command in backquotes is a find command that builds a list of chapter files in
the /work directory. That list is then used to provide the set of input files
for grep to search for titles. The output is saved in a file called chaptitles.

5. Look inside a non-text file. Sometimes you really want to see
inside a binary file. Maybe there isn't a manpage and you're looking for usage
information, or perhaps you're looking for information about who wrote a program
or what application a file is associated with.
The strings command is
perfect for that purpose--it searches through a file looking for sequences of
printable character strings and writes them to standard output. You can pipe the
output through a pager like more, or if you are looking for particular text, you
can pipe the output to the grep command.

6. Use the locate
command. Looking for an easier way to find files than the find command? Try
using locate. In contrast to find's complexity, locate is the ultimate in
simplicity. The command:
locate

searches an
internal database and prints the pathnames of all files and directories that
contain the given string in their names. You can narrow down the search by
piping the output to grep. For example, the following finds all files containing
the string "kde" that are in bin directories:

locate kde grep
bin

The strings don't have to be complete names; they can be
partial strings, such as "gno" instead of spelling out "gnome". The -r option
lets you use a regular expression (in quotes):

locate -r 'gno*'

One thing to be aware of is that locate is case-sensitive:
Searching for HOWTO and for howto will give you different results.

Rather than searching the disk each time, as find does, locate
depends on the creation and maintenance of a database. Because it only has to
search the database, not the disk, locate is faster than find. On the other
hand, the results are only as current as the database.

The locate
database is generally updated daily by a cron job, but you can update it
manually by running the command updatedb (usually as root). If you are adding
new applications or deleting old files and you don't want to wait for the next
day to have an up-to-date database, you might want to run it manually.

7. Use dmesg to view startup messages. The dmesg command provides
an easier way to see the boot messages than trying to read them before they
scroll off the screen. When Linux boots, the kernel startup messages are
captured in a buffer known as the kernel ring buffer; dmesg prints the contents
of that buffer. By default, dmesg prints its output to the screen; you can of
course redirect the output to a file:
% dmesg > bootmsg

8.
Find out what kernel version you are using. Do you ever need to know what
version of the Linux kernel is running on your system? You can find out with the
uname command, which prints information about the system. Issued with the -r
option, uname prints the kernel version:
% uname -r
2.2.14-5.0

Other uname options provide information such as the machine type,
the name of the operating system, and the processor. The --all option prints all
the available information.

9. Use df and du to maintain your disk.
Use the df (display filesystem) command to keep an eye on how much space each of
your filesystems occupies and how much room is left. It's almost inevitable that
if you like to download new software and try it out, you'll eventually fill up
your disk. df has some options, but running it without options provides the
basic information--the column labeled Use% tells you how full each filesystem
is:
% df Filesystem 1k-blocks Used Available Use% Mounted on /dev/hda3
1967156 1797786 67688 96% /

Oops, time to clean house... and
that's where du (disk usage) comes in handy. The du command provides the
information you need to find the big space users, by printing the amount of disk
space used for each file, subdirectory, and directory. You can specify the
directory du is to start in, or let it default to the current directory.

If you don't want to run du recursively through subdirectories,
use the -s option to summarize. In that case, you need to specify all the
directories you are interested in on the command line. For example:

% du -s /usr/X11R6
142264 /usr/X11R6

% du -s
/usr/X11R6/*
34490 /usr/X11R6/bin
1 /usr/X11R6/doc
3354
/usr/X11R6/include

97092 /usr/X11R6/lib
7220
/usr/X11R6/man
106 /usr/X11R6/share

With the information provided by du, you can start in the directories that occupy the most disk space and delete or archive files you no longer actively use.

10. Permit non-root users to mount or unmount drives. While hard drives are normally mounted automatically when the system is booted, other drives such as the floppy
drive and the CD-ROM are generally not mounted until they are going to be used,
so that disks can be inserted and removed. By default, root privileges are
required for doing the mount (or unmount). However, you can modify the entries
in the filesystem table, /etc/fstab, to let other users run the mount command.
Do this by adding the option "user" to the appropriate entry:
/dev/fd0
/mnt/floppy auto noauto,user 0 0 /dev/cdrom /mnt/cdrom iso9660
noauto,ro,user,unhide 0 0

You can see what filesystems are
currently mounted, and what options they were mounted with, by looking at the
file /etc/mtab or by running the mount command with no options or arguments.

Linux Commands and Shell Commands

2007-09-09T07:41:00.000-07:00

Linux Command Line Tools - The Top 50:

Managing Software with yum

2007-09-08T22:43:00.000-07:00

Managing Software with yum:

Forum: Simple Machines Forum

2007-09-08T11:36:00.001-07:00

Simple Machines Forum:

TBD

So You'd Like To Use MySQL

2007-09-08T06:02:00.000-07:00

So You'd Like To Use MySQL...
Getting Started with the World's Most Popular Open Source Database

In this article, Jon Stephens shares how you can obtain and install a MySQL database for your Linux system. He provides lots of beginner instructions including use of the MySQL Monitor, a tool for using and adminstering MySQL that's part of the basic distribution. The article also delves into the introduction for securing your MySQL database. Written to encourage further use of LAMP (Linux/Apache/MySQL/PHP), the article helps anyone apply the power of MySQL in their business.
Table of Contents
What is MySQL?
How I Get MySQL? How Do I Install It?
Securing Your New Installation
What's Next?
Errors & Troubleshooting

Forum: Whirlpool Australian Broadband Discussion Forums

2007-09-08T05:58:00.000-07:00

Linux/BSD

TBD

What is CentOS?

2007-09-08T05:40:00.000-07:00

CentOS, from Wikipedia:

CentOS is a freely available Linux distribution which is based on Red Hat's commercial Red Hat Enterprise Linux (RHEL) product. This rebuild project strives to be 100% binary compatible with the upstream product and, within its mainline and updates, not to vary from that goal. Additional software archives hold later versions of such packages, along with other Free and Open Source Software RPM based packages. CentOS stands for Community ENTerprise Operating System.

RHEL is largely composed of free and open source software, but is made available in a usable, binary form (such as on CD-ROM or DVD-ROM) only to paying subscribers. As required, Red Hat releases all source code for the product publicly under the terms of the GNU General Public License and other licenses. CentOS developers use that source code to create a final product which is very similar to RHEL and freely available for download and use by the public, but not maintained or supported by Red Hat. There are other distributions derived from RHEL's source as well, but they have not attained the surrounding community which CentOS has built; CentOS is generally the one most current with Red Hat's changes.

CentOS' preferred software updating tool is based on yum, although support for use of an up2date variant exists. Each may be used to download and install both additional packages and their dependencies, and also to obtain and apply periodic and special (security) updates from repositories on the CentOS Mirror Network.

CentOS can be used as an X Window System based desktop but, like RHEL, is targeted primarily at the server market. Some hosting companies rely on CentOS working together with the cPanel Control Panel.

Website: http://centos.org
Company: CentOS
Developer: Lance Davis
OS family: Linux
Source model: Free software
Latest stable release: 5.0 / April 12, 2007
Kernel type: Monolithic kernel, Linux
License: Various Working state: in development

Finding Linux Commands Quickly using Man or Info

2007-09-08T05:38:00.000-07:00

Finding Commands Quickly using Man or Info:

I was looking at a man page yesterday, but I cannot remember the name of the command I was reading about, and I did not write it down. How do I get the man page back?
The command you used is stored in a file called .bash_history. By default, this file records the last 500 commands you typed at the shell prompt.
You can glimpse the history of your commands by typing history at the shell prompt, but the results are displayed too quickly for you to read every line.
Another way to view .bash_history is with a utility such as less. Type less .bash_history at the shell prompt and the results will display one page at a time. To move forward a screen, press the [Space] bar; to move back a screen, press the [b] key, and to quit, press [q].
Paging through .bash_history to find a command can be tedious. Alternatively, you can search through the file for keywords using grep, a powerful search utility.
Say you were reading the man page the day before, but cannot recall its name. To search for the command, type:
history | grep man
All the commands you typed which have the word man in them are now highlighted.
There are many ways to use your command history. For other tips and tricks, see Section 14.8 Tips on Using Command History.

Primary TCP/IP Port Assignments and Descriptions

2007-09-08T02:13:00.000-07:00

Primary TCP/IP Port Assignments and Descriptions:

TCP/IP provides a total of 65,535 ports of which 1023 are considered to be well known ports. In reality the number of ports that are used by popular network clients and services comprises an even smaller subset of the well known group of ports. The following table lists the functions of this subset.

Port	Assigment	Description
20	FTP	File Transfer Protocol (Data) - The File Transfer protocol provides a mechanism for transferring specific files between network connected computer systems (usually a Linux or UNIX based system). Transfer is typically performed using the ftp client which provides a range of commands used to connect to a remote server for the purpose of uploading or downloading files. Most modern web browsers also have the ability to browse and download files located on a remote FTP server. FTP uses TCP (rather than UDP) to transfer files so is considered to be a highly reliable transport mechanism. FTP does not encrypt data and is not considered to be a secure file transfer protocol. The use of Secure Copy Protocol (SCP) and Secure File Transfer Protocol (SFTP) is strongly recommended in place of FTP.
21	FTP	File Transfer (Control) - Traditionally FTP has two ports assigned (port 20 and port 21). Port 20 was originally conisidered the data transfer port, while port 21 was assigned to communicate control information. In modern implementations port 20 is now rarely used, with all communication taking place on port 21.
22	SSH	Secure Shell - The Secure Shell is used to provide a secure, encypted, remote logon session to a remote host over a TCP/IP network. The original mechanism for remote access was the Telnet protocol. Because Telnet transmits data in plain text its use is now strongly discouraged in favor of the secure shell, which encrypts all communications, including log-in and password credentials. SSH also provides the mechanism by which files can be securely trandferred using the Secure Copy Protocol (SCP), and is also the basis for the Secure File Transfer Protocol (SFTP). SSH also replaces both the rsh and rlogin clients.
23	Telnet	Telnet - Telnet is a terminal emulation protocol that provides the ability to log into a remote system over a TCP/IP connection. The access is text based allowing the user to type into a command prompt on the remote host and text displayed by the remote host is displayed on the local Telnet client. Telnet encrypts neither the password nor the text communicated between the client and server. As such, the use of telnet is strongly discouragaed. Most modern systems will have port 23 closed and the telnet service disabled to prevent its use. SSH should be used in place of Telnet.
25	SMTP	Simple mail Transfer Protocol - SMTP defines the mechanism by which email messages are sent from one network host to another. SMTP is a very simple protocol and requires that the mail service always be available at the receiving host. Typically the receiving host will store incoming messages in a spool for subsequent access by the recipient using the POP3 or IMAP protocols. SMTP uses the TCP transport protocol to ensure error free message delivery.
53	DNS	Domain Name Server - The service used by TCP/IP networks to translate host names and Fully Qualified Domain Names (FQDN) to IP addresses.
69	TFTP	Trivial File Transfer Protocol - TFTP is a strpped down version of the File Transfer Protocol (FTP). It has a reduced command-set and lacks authentication. The most significant feature of TFTP is that it uses UDP to transfer data. This results in extremely fast transfer speeds but, consequently, lacks data reliability. TFTP is typically used in network based booting for diskless workstations.
80	HTTP	Hypertext Text Transfer Protocol - HTTP is the protocol used to download text, graphics and multimedia from a web server and to a web browser. Essentially it defines the command and control mechanism between the browser and server defining client requests and server responses. HTTP is based on the TCP transport protocol and, as such, is a connection-oriented protocol.
110	POP3	Post Office Protocol - The POP3 protocol is a mechanism for storage and retrieval of incoming email messages from a server. In most corporate environments incoming email is stored on an email server and then downloaded to an email client running on the user's desktop or laptop when the user checks email. POP3 downloads all new messages to the client, and does not provide the user the option of choosing which messages to download, view headers, or download only parts of messages. It is for this reason the IMAP protocol is increasingly being used in place of POP3.
119	NNTP	Network News Transfer Protocol - The protocol responsible for posting and retrieving messages to and from Usenet News Servers (i.e newsgroups and discussion forums hosted on remote servers). NNTP operates at the Application layer of the OSI stack and uses TCP to ensure error free message retrieval and transmission.
123	NTP	Network Time Protocol - A protocol designed to synchronize computer clocks with an external time source. Using this protocol an operating system or application can request the current time from a remote NTP server. The remote NTP server is usually based on the time provided by a nuclear clock. NTP is useful for ensuring that all systems in a network are set to the same, accurate time of day. This is of particular importance in security situations when, for example, the time a file was accessed or modified on a client or server is in question.
143	IMAP4	Internet Message Access Protocol, Version 4 - IMAP4 is an advanced and secure email retrieval protocol. IMAP is similar to POP3 in that it provides a mechanism for users to access email messages stored on an email server, although IMAP includes many additional features such as the ability to selectively download messages, view message headers, search messages and download part of a message. IMAP4 uses authentication and fully supports Kerberos authentication.
161	SNMP	Simple Network Management Protocol - Provides a mechanism whereby network administrators are able to collect information about the devices (such as hubs, bridges, routers and switches) on a network. The SNMP protocol enables agents running on network devices to communicate their status to a central manager and, in turn, enables the manager to send new configuration parameters to the device agent. The agents can further be configured to notify the manager when certains events, known as traps, occur. SNMP uses UDP to send and receive data.
443	HTTPS	Hypertext Transfer Protocol Secure - The standard HTTP (non-secure) protocol transfers data in clear text (i.e with no encryption and visible to anyone who might intercept the traffic). Whilst this is acceptable for most web browsing purposes it poses a serious security risk when confidential information such as credit card details need to be transmitted from the browser to the web server. HTTPS addresses this by using the Secure Sockets Layer (SSL) to send encypted data between the client and server.
2049	NFS	Network File System - Originally developed by Sun Microsystems and subsequently widely adopted throughout the industry, NFS allows a file system on a remote system to be accessed over the network by another system as if the file system were on a local disk drive. NFS is widely used on UNIX and LINUX based systems. Later versions of Microsoft Windows possess the ability to also access NFS shared file systems on UNIX and LINUX based systems.

Best JavaScript Resources

2007-09-08T02:06:00.000-07:00

JavaScript Essentials on TechTopia.com:

* About this Book
* Intended Audience

1. The History of JavaScript
* Jim and Marc Meet in Palo Alto
* Moving on from Static Web Pages
* LiveScript, JavaScript, JScript, ECMAScript - What's in a Name?
2. A Simple JavaScript Example
3. Embedding JavaScript into Web pages
* The element
* Where to place JavaScript in a Web Page
4. Introducing JavaScript Variables
* Variable Declaration and the Assignment Operator
* JavaScript Variable Naming Conventions
5. JavaScript Variable Types
* The JavaScript typeof Operator
6. JavaScript Operators
* Assignment Operators
* Arithmetic Operators
* Unary Operators - Incrementing and Decrementing Variable Values
* Comparison Operators
* String Operators
* Conditional Operators
* Logical Operators
7. Comments in JavaScript
* Single Line Comments
* Multi-line Comments
8. JavaScript Flow Control and Looping
* JavaScript Conditional Statements
* The JavaScript if Statement
* The JavaScript if ... else Statements
* JavaScript Looping Statements
* JavaScript for loops
* JavaScript while loops
* JavaScript do ... while loops
* JavaScript switch Statements
* Breaking a Loop
* label Statements
* Skipping Statements in Current Loop Iteration
9. Understanding JavaScript Functions
* Declaring and Calling a JavaScript Function
* Passing Arguments to a Function
* Returning a Value from a Function
* Where to Place Function Declarations
10. JavaScript Object Basics
* Creating a Custom JavaScript Object
* Creating and Using Object Instances
* Extending JavaScript Objects
11. JavaScript String Object
* Creating a JavaScript String Object
* JavaScript String Object Methods
* JavaScript String Object Properties
* JavaScript String Object Examples
* Getting the length of a String Object
* Setting String Object text Effects
* Performing Conversions on String Objects
* Manipulating Strings with the String Object
12. JavaScript Date Object
* Understanding System Time
* Creating a JavaScript Date Object
* Setting the Time and Date of the JavaScript Date Object
* Reading the Date and Time from a JavaScript Date Object
* UTC Time
* Finding the Time Zone Offset and Getting Local Time
13. JavaScript Math Object
* JavaScript Math Object Methods
* JavaScript Math Object Properties
* Using JavaScript Math Object and Properties
* Rounding and Truncating Numbers with the the Math Object
14. JavaScript Window Object
* Referencing the JavaScript window Object
* JavaScript window Object Properties
* Opening Browser Windows using JavaScript
* Closing Browser Windows using JavaScript
* Moving and Resizing Windows
* Changing Window Focus
* Displaying Message Box Dialogs
15. JavaScript Document Object
* What is the JavaScript Document Object?
* JavaScript Document Object Methods and Properties
* Using the JavaScript Document Object
* Writing text to a document
* Writing Text to a document in a different Window
* Changing the Document Title
* Changing the Document Colors
* Getting a List of Objects in a Document
16. JavaScript Location Object
* Loading a New URL into the Current Window
* Reading the URL of the Current Window
* Extracting Parts of the URL
* JavaScript Location Object Methods
17. JavaScript History Object
18. JavaScript Arrays
* What is a JavaScript Array
* How to Create a JavaScript Array
* Initializing the Elements of an Array
* Accessing the Elements of a JavaScript Array
* JavaScript Array Object Methods and Properties
* JavaScript Array Sorting
19. JavaScript Timeouts
* Setting up a JavaScript Timeout
* Cancelling a JavaScript Timeout
* Setting up JavaScript Timeout to Repeat
20. Building Forms with JavaScript
* The JavaScript Form Object
* Accessing Objects in a Form
* The JavaScript Text Object
* JavaScript TextArea Object
* The JavaScript Button Object
* JavaScript Check Boxes
* JavaScript Radio Buttons
* JavaScript Drop-down / Select Object
* Obtaining the Current Selection from the JavaScript Select Object
* JavaScript Password Object
21. Understanding JavaScript Cookies
* What is a JavaScript Cookie?
* The Structure of a Cookie
* Cookie Name / Value Pair
* Cookie Expiration Setting
* Cookie path Setting
* Cookie domain Setting
* Creating a Cookie
* Reading a Cookie
* Removing a Cookie
22. Understanding Cascading Style Sheets (CSS)
* What are Cascading Style Sheets for?
* Embedding CSS Styles into a Web Page
* Importing an External Style Sheet into a Web Page
* Creating CSS Rules
* Setting Styles for Individual Elements
* Setting Styles using the id Attribute of an HTML Element
* Using Classes with CSS Rules
23. JavaScript and CSS - Dynamic Styles and Layers
* Making Basic Dynamic Style Changes
* Hiding and Showing Content Using JavaScript
* Using Overlaying Layers
* Making Layers Move

Best PHP Resources

2007-09-08T02:01:00.000-07:00

PHP Essentials on techotopia.com:

Best Linux Resources

2007-09-08T01:51:00.000-07:00

Linuxtopia.org

Technical Library
How-To Guides
Search (over 16,000 pages of detailed technical information)

Glossary of Basic Linux / CentOS Commands

2007-09-08T01:41:00.000-07:00

From A Comparison of Common DOS and Linux Commands:

Many Linux commands typed at a shell prompt are similar to the commands you would type in DOS. In fact, some commands are identical.
This appendix provides common commands used at the DOS prompt in Windows and their counterparts in Linux. Basic examples of how the command are used at the Linux shell prompt are also provided. Note that these commands usually have a number of options. To learn more about each command, read its associated man page (for example, type man ls at the shell prompt to read about the ls command).

Command's Purpose	MS-DOS	Linux	Basic Linux Example
Copies files	`copy`	`cp`	`cp thisfile.txt /home/thisdirectory`
Moves files	`move`	`mv`	`mv thisfile.txt /home/thisdirectory`
Lists files	`dir`	`ls`	`ls`
Clears screen	`cls`	`clear`	`clear`
Closes shell prompt	`exit`	`exit`	`exit`
Displays or sets date	`date`	`date`	`date`
Deletes files	`del`	`rm`	`rm thisfile.txt`
"Echoes" output to the screen	`echo`	`echo`	`echo this message`
Edits text files	`edit`	`gedit`([a])	`gedit thisfile.txt`
Compares the contents of files	`fc`	`diff`	`diff file1 file2`
Finds a string of text in a file	`find`	`grep`	`grep word or phrase` `thisfile.txt`
Formats a diskette	`format a:` (if diskette is in `A:`)	`mke2fs`	`/sbin/mke2fs /dev/fd0` (`/dev/fd0` is the Linux equivalent of `A:`)
Displays command help	`command /?`	`man` or `info`	`man command`
Creates a directory	`mkdir`	`mkdir`	`mkdir directory`
Views contents of a file	`more`	`less`([b])	`less thisfile.txt`
Renames a file	`ren`	`mv`([c])	`mv thisfile.txt thatfile.txt`
Displays your location in the file system	`chdir`	`pwd`	`pwd`
Changes directories with a specified path (absolute path)	`cd pathname`	`cd pathname`	`cd /directory/directory`
Changes directories with a relative path	`cd..`	`cd ..`	`cd ..`
Displays the time	`time`	`date`	`date`
Shows amount of RAM in use	`mem`	`free`	`free`
Notes: a. Gedit is a graphical text editor; other editors you can use in place of Gedit include nano and `vi`. b. The `more` pager can also be used to page through a file one screen at a time. c. The `mv` command can both move a file and, if you want to rename a file in the same directory, "move" that file to the same directory with a new name.

Table D-1. Similar Commands

Are Linux commands universal across distributions?

2007-09-08T01:38:00.000-07:00

From 3 Reasons to Learn Linux Commands in Multiple Linux Distributions - Linux Training Online:

Are you just new to Linux? Are you confused about which Linux distribution to learn for your Linux system administration career?

Here's the great news! Linux commands are virtually identical from one Linux distribution (a.k.a.version, distro) to another.

So, when you learn a Linux command in one Linux distribution, you have learned that command for ALL Linux distributions.

Linux Tips: The Linux commands we're talking about here are the very popular GNU / Linux commands that are common to every Linux distribution. These are the essential Linux commands required for Linux system administration, like the cd, ls, cp, rm, pwd and mkdir commands.

Linux kernel

2007-08-20T04:48:00.002-07:00

Source: http://en.wikipedia.org/wiki/Linux_kernel

The Linux kernel is a Unix-like operating system kernel. It is the namesake of the Linux family of operating systems. Released under the GNU General Public License (GPL) and developed by contributors worldwide, Linux is one of the most prominent examples of free and open source software.^[3]

Linux was written by Linus Torvalds in 1991. Early on, the Minix community contributed code and ideas to the Linux kernel. At the time, the GNU Project had created many of the components required for a free software operating system, but its own kernel, GNU Hurd, was incomplete and unavailable. The BSD operating system had not yet freed itself from legal encumbrances. This meant that despite the limited functionality of the early versions, Linux rapidly accumulated developers and users who adopted code from those projects for use with the new operating system.^[4] Today the Linux kernel has received contributions from thousands of programmers.

Linux

2007-08-20T04:48:00.001-07:00

Source: http://en.wikipedia.org/wiki/Linux

Linux (IPA pronunciation: /ˈlɪnʊks/) is a Unix-like computer operating system. Linux is one of the most prominent examples of free software and open source development; its underlying source code can be freely modified, used, and redistributed by anyone.^[1]

Web Server

2007-08-18T07:52:00.000-07:00

Wikipedia.org: http://en.wikipedia.org/wiki/Web_server

The term Web server can mean one of two things:
1. A computer program that is responsible for accepting HTTP requests from clients, which are known as Web browsers, and serving them HTTP responses along with optional data contents, which usually are Web pages such as HTML
documents and linked objects (images, etc.).
2. A computer that runs a computer program which provides the functionality described in the first sense of the term.

TBD

Article: Apache with Quad Cores

2007-08-18T07:45:00.001-07:00

SOURCE: http://www.tummy.com/Community/Articles/benchmark-quadcore-apache/

Article: The Perfect Setup - CentOS 5.0 (32-bit)

2007-08-18T07:41:00.001-07:00

SOURCE: http://www.howtoforge.com/perfect_setup_centos5.0

Web Admin 101

2007-08-18T07:34:00.000-07:00

I'm starting this blog to take notes on my research on how to perform web server administration.