Friday, December 11, 2009

Creating a Swap File

To add a swap file:

  1. Determine the size of the new swap file in megabytes and multiply by 1024 to determine the number of blocks. For example, the block size of a 64 MB swap file is 65536.

  2. At a shell prompt as root, type the following command with count being equal to the desired block size:

    dd if=/dev/zero of=/swapfile bs=1024 count=65536
  3. Setup the swap file with the command:

    mkswap /swapfile
  4. To enable the swap file immediately but not automatically at boot time:

    swapon /swapfile
  5. To enable it at boot time, edit /etc/fstab to include the following entry:

    /swapfile          swap            swap    defaults        0 0

    The next time the system boots, it enables the new swap file.

  6. After adding the new swap file and enabling it, verify it is enabled by viewing the output of the command cat /proc/swaps or free.

Extending Swap on an LVM2 Logical Volume

To extend an LVM2 swap logical volume (assuming /dev/VolGroup00/LogVol01 is the volume you want to extend):

1. Disable swapping for the associated logical volume:

# swapoff -v /dev/VolGroup00/LogVol01

2. Resize the LVM2 logical volume by 256 MB:

# lvm lvresize /dev/VolGroup00/LogVol01 -L +256M

3. Format the new swap space:

# mkswap /dev/VolGroup00/LogVol01

4. Enable the extended logical volume:

# swapon -va

5. Test that the logical volume has been extended properly:

# cat /proc/swaps # free

Thursday, June 11, 2009

Linux to help animals

Active Media Products just released the perfect gift for Linux nerds young and old.

The actual product wasn't made with Linux users in mind. Active Media teamed up with the WWF ( World Wildlife Fund) to make a bunch of USB drives themed after endangered animals. A portion of the proceeds from sales will go to the WWF to help stop cute animals such as Penguin from dying out.

There are four different versions of the Penguin USB drive available; 2GB, 4GB, 8GB, and 16GB versions. The 8GB version will retail for around $26 dollars, and all versions are available right now from and other retailers.

USB - Pen Drive 19
Dog style shape of USB pen drive.

USB - Pen Drive 20
penguin shape of USB pen drive.

USB - Pen Drive 21
Multi-penguin shape of USB pen drive.

USB - Pen Drive 22
Teddy bear shape of USB pen drive.

USB - Pen Drive 23

Tuesday, May 19, 2009

How to Create a swap file in Linux partition

Linux divides its physical RAM (random access memory) into chucks of memory called pages. Swapping is the process whereby a page of memory is copied to the preconfigured space on the hard disk, called swap space, to free up that page of memory. The combined sizes of the physical memory and the swap space is the amount of virtual memory available.

Swapping is necessary for two important reasons. First, when the system requires more memory than is physically available, the kernel swaps out less used pages and gives memory to the current application (process) that needs the memory immediately. Second, a significant number of the pages used by an application during its startup phase may only be used for initialization and then never used again. The system can swap out those pages and free the memory for other applications or even for the disk cache.

Steps to create swap file

1. Use the "dd" command to create a file.

dd if=/dev/zero of=/aSwapFile bs=1024 count=65536

where dd: - is used to copy a specified number of bytes from an Input file (if) to an Output file (of).
Here the dd command copy null characters from the special file "/dev/zero" and copy it to the output file "aSwapFile" in the "/" directory. The "bs" specifies that the characters are read as BYTES. The "count" specifies the size of the bytes block that is to be created in the output file.

2. Use the "mkswap" command to set up the Linux swap area on the file created.

mkswap /aSwapFile

3. Use the "swapon" command to activate the swap file created.

swapon /aSwapFile

4. Edit the fstab "/etc/fstab" to enable the swap after a reboot.

vi /etc/fstab
(Add the following line to the fstab file.)
/aSwapFile swap swap defaults 0 0

Thursday, May 14, 2009

Batch file renaming

Batch file renaming can be pretty handy as it saves loads of time when you have to rename thousands of files. There are many simple ways to do it though.

If you have files with same ending pattern it can be done as:

e.g. if you want all .htm to be renamed to .html

rename .htm .html *.htm

and On other Unixes, we'd have to do something like this to batch rename files:

for i in *.html
j=`echo $i | sed 's/.htm$/.html/'`
# or, in this simple case even just: j=$"i"l
mv $i $j

Though if we had bash or ksh, we could make that a little less cumbersome:

for i in *.htm
# or: j=${i}l
mv $i $j

The Linux "rename" isn't going to handle to more complex cases though. For example, I had to transfer mail files from one system to another recently. On the old system, each message would be named something like "1124993500.7359464636.e-smith". On the new system, they'd be "00000001.eml", with hexadecimal numbering going on up, so you'd get "00000009.eml" and the next message would be "0000000a.eml", and so on. There's no way for "rename" to do that, but a loop can:

for i in *
j=`printf "%0.9x.eml\n" $x`
mv $i $j

And if you dont want to follow any pattern and simply add new extension to all the files in a directory:

for i in $(ls -lArt /path/to/directory |awk '{print $9}');do mv $i $i.txt; done

adding to it if files are placed recursively in directories:

for i in $(find /path/to/root -type f -print);do mv $i $i.txt; done

Using Foremost

Foremost Syntax

foremost [-h][-V][-d][-vqwQT][-b][-o

] [-t][-s][-i]

Available Options

-h Show a help screen and exit.
-V Show copyright information and exit.
-d Turn on indirect block detection, this works well for Unix file systems.
-T Time stamp the output directory so you don’t have to delete the output dir when running multiple times.
-v Enables verbose mode. This causes more information regarding the current state of the program to be dis-played on the screen, and is highly recommended.
-q Enables quick mode. In quick mode, only the start of each sector is searched for matching headers. That is,the header is searched only up to the length of the longest header. The rest of the sector, usually about 500 bytes, is ignored. This mode makes foremost run con- siderably faster, but it may cause you to miss files that are embedded in other files. For example, using quick mode you will not be able to find JPEG images embedded in Microsoft Word documents.

Quick mode should not be used when examining NTFS file systems. Because NTFS will store small files inside the Master File Table, these files will be missed during quick mode.

-Q Enables Quiet mode. Most error messages will be sup-pressed.
-w Enables write audit only mode. No files will be extracted.
-a Enables write all headers, perform no error detection in terms of corrupted files.
-b number Allows you to specify the block size used in foremost. This is relevant for file naming and quick searches. The default is 512. ie. foremost -b 1024 image.dd

-k number Allows you to specify the chunk size used in foremost.This can improve speed if you have enough RAM to fit the image in. It reduces the checking that occurs between chunks of the buffer. For example if you had > 500MB of RAM. ie. foremost -k 500 image.dd

-i file The file is used as the input file. If no input file is specified or the input file cannot be read then stdin is used.

-o directory Recovered files are written to the directory directory.

-c file Sets the configuration file to use. If none is speci-fied, the file “foremost.conf” from the current direc-tory is used, if that doesn’t exist then “/etc/fore-most.conf” is used. The format for the configuration file is described in the default configuration file included with this program. See the CONFIGURATION FILE section below for more information.

-s number Skips number blocks in the input file before beginning the search for headers. ie. foremost -s 512 -t jpeg -i /dev/hda1

Foremost examples

Search for jpeg format skipping the first 100 blocks

sudo foremost -s 100 -t jpg -i image.dd

Only generate an audit file, and print to the screen (verbose mode)

sudo foremost -av image.dd

Search all defined types

sudo foremost -t all -i image.dd

Search for gif and pdf

sudo foremost -t gif,pdf -i image.dd

Search for office documents and jpeg files in a Unix file sys-tem in verbose mode.

sudo foremost -v -t ole,jpeg -i image.dd

Run the default case

sudo foremost image.dd

image.dd means you need to enter your hardisk mount point i.e /dev/sda1 or /dev/sda2

Recover deleted files in Linux

Although there's no common "undelete" command for a Linux EXT3 file system, you can recover many types of accidentally erased files, including documents, graphics, and system files using the "Foremost" console application.

When you delete a file, the data is not really overwritten. The pointer in the filesystem to the file is simply removed so the disk area can be overwritten when necessary. The more the disk is written to after the file is deleted, the larger the chance it will be overwritten and become unrecoverable.

Foremost is a command line utility for finding and recovering deleted files based on their type. It was origionally developed for the US Air Force Office of Special Investigations. It can recover files from a number of filesystems, including fat, ext3 and NTFS. It can be installed and run from the live cd.

Foremost can recover files with the following extensions:
jpg, gif, png, bmp, avi ,exe, mpg, wav, riff, wmv, mov, pdf, ole, Excel, Access, doc, zip, XML, SXW, SXC, SXI, SX, rar, htm, cpp

For other file extensions we may need to edit /etc/foremost.conf which can be found in man page of Foremost (man foremost)

How to Install:

Enable the universe repository and install foremost:

sudo apt-get install foremost

Assuming the lost files are on a USB drive (sda), you need to create a writeable directory on another drive where you can put the recovered files

sudo mount /dev/sdb1 /recovery
sudo mkdir /recovery/foremost

And then run foremost:

sudo foremost -i /dev/sda -o /recovery/foremost

or for specific file format e.g. video (avi):

sudo foremost -t avi -i /dev/sda -o /recovery/foremost

The recovered files will then be owned by root. Change their ownership so that you can use them:

sudo chown -R youruser:yourgroup /recovery/foremost

Please note that there's no guarantee that foremost will succeed in recovering your files, but at least there's a chance.

Up to 24 percent of software purchases open source

Open source has become big business, suggests an article in the Investors Business Daily, but it has done so by becoming more like the proprietary-software world it purports to leave behind.

The article cites recent research from IDC indicating that CIOs allocated up to 24 percent of their budgets to open-source software in 2008, up from 10 percent in 2007--a finding that jibes with recent data from Forrester. This open-source growth is propelling Red Hat to grow "at two to three times the rate of the broader software industry over a multiyear horizon," according to research from Piper Jaffray.

Monday, May 11, 2009

Tools to access Linux Partitions from Windows

If you dual boot with Windows and
Linux , and have data spread across different partitions on Linux and Windows, you should be really in for some issues.

It happens sometimes you need to access your files on Linux partitions from Windows, and you realize it isn’t possible easily. Not really, with these tools in hand - it’s very easy for you to access files on your Linux partitions from Windows.

  • Explore2fs

Explore2fs is a GUI explorer tool for accessing ext2 and ext3 filesystems. It runs under all versions of Windows and can read almost any ext2 and ext3 filesystem.

Project Home Page :-

Latest Version :- 1.07

Sample Screenshot

  • DiskInternals Linux Reader

DiskInternals Linux Reader is a new easy way to do this. This program plays the role of a bridge between your Windows and Ext2/Ext3 Linux file systems. This easy-to-use tool runs under Windows and allows you to browse Ext2/Ext3 Linux file systems and extract files from there.

Project Home Page :-

Latest Version :- 1.0

Sample Screenshot

  • Ext2 Installable File System for Windows

It provides Windows NT4.0/2000/XP/2003 with full access to Linux Ext2 volumes (read access and write access). This may be useful if you have installed both Windows and Linux as dual boot environment on your computer.

Project Home Page :-

Latest Version :- 1.10c

Sample Screenshot

  • rfsd: ReiserDriver

ReiserDriver is an Installable File System Driver (IFSD), used to easily (and natively!) read ReiserFS disk partitions under Microsoft Windows(2K/XP) by allowing ReiserFS partitions to appear as additional disks to the Windows operating system.

Project Home Page :-

Latest Version :- 1.

Wednesday, May 6, 2009

Restricting Remote Logins to listed users

To restrict remote logins to specific users, do the following:

1. Create a file called /etc/remusers with the names of the users, that are allowed to perform remote logins. It can look like:


2. Modify the /etc/profile and /etc/csh.login files by adding the code listed below.

Putting the following code in /etc/profile and /etc/csh.login will keep users not listed in the file /etc/remusers from being able to login from remote location or telnet session. Be sure carriage returns are not included in the script files when you add the below code to them or the scripts will not run correctly, giving strange errors. Carriage returns are many times accidently embedded when code is copied from Windows or DOS based machines to Linux based machines.

  1. trap "" 2 3
  2. if { $LOGNAME != "root" ]
  3. then
  4. if [ $TERM != "linux" ]
  5. then
  6. if [ -z `cat /etc/remusers |grep $LOGNAME` ]
  7. then
  8. echo " *************************************************** "
  9. echo " * * "
  10. echo " * Remote logins are not allowed on this system * "
  11. echo " * Please use a terminal or see the administrator. * "
  12. echo " * Press RETURN to exit. * "
  13. echo " * * "
  14. echo " *************************************************** "
  15. echo
  16. read
  17. exit
  18. fi
  19. fi
  20. fi
  21. trap 2 3

Line 1 traps SIGINT and SIGQUIT, so users cannot abort the script. Line 2 is a safety, in case you change the /etc/profile before you create the /etc/remusers file. Line 4 only runs the script if the terminal is not local. The "linux" terminal type is used locally. You may need to change this to:

if [ $TERM == "vt100" ]

if you are using serial terminals also. As an alternate, add another if statement that excludes the serial terminal type inside the first if statement to exclude both serial terminals and local terminals. You can determine what terminal type is being used by looking at the value of the TERM variable with the env command after logging in from the terminal in question. Also there are various types of terminals that telnet clients may emulate, so, you will want to be sure not to allow any terminals that a telnet client can emulate.

Line 6 determines if the user who just logged in, $LOGNAME, is listed in the /etc/remusers file. Line 16 reads a line from the user, requiring them to press an end of line key such as RETURN. Line 17 causes the shell to exit.

Linux Configuration and Diagnostic Tools

System and Network Configuration

  • linuxconf - A GUI interactive interface available on Redhat 6.0 or later which includes netconf configuration.
  • netconf - A GUI interactive interface available on Redhat 6.0 and later.
  • kbdconf - A Redhat Linux tool which configures the /etc/sysconfig/keyboard file which specifies the location of the keyboard map file. This is a GUI based tool.
  • mouseconfig - A Redhat Linux tool used to configure the /etc/sysconfig.mouse file. This is a GUI tool.
  • timeconfig - A Redhat Linux tool used to configure the /etc/sysconfig/clock file. This is a GUI tool used to set timezone and whether or not the clock is set to GMT time.
  • kernelcfg - A Redhat kernel configuration utility to be started from X.
  • stty - Used to configure and print the console devices.
  • setterm - Set terminal attributes.
  • vmstat - Report statistics on virtual memory.

X Configuration

  • XF86Setup - A newer X configuration program with a GUI interface which modifies the "/etc/X11/XF86Config" configuration file.
  • xf86config - An older X configuration program with a text based interface. It also modifies the "/etc/X11/XF86Config" configuration file.
  • Xconfigurator - The Redhat tool used during system setup to configure X.
  • SuperProbe - A program that probes the video card to determine its type for use with setting up X.
  • xvidtune - This program will test video modes on the fly without modification to your X configuration. Read the usr/X11R6/lib/X11/doc/VideoModes.doc file before running this program.

Library and kernel Dependency Management

Library management:

  • ldd - Used to determine shared libraries used by binary files. Type "ldd /bin/ls" to see the shared libraries used by the "ls" command.
  • ldconfig - Used to update links and cache for system use of the most recent runtime shared libraries.

Kernel Management:

  • lsmod - List currently installed kernel modules.
  • depmod - Creates a dependency file, "modules.dep" in the directory "/lib/modules/x.x.x", later used by modprobe to automatically load the relevant modules.
  • insmod - Installs a loadable kernel module into the running kernel.
  • rmmod - Unloads modules, Ex: rmmod ftape
  • modprobe - Used to load a module or set of modules. Loads all modules specified in the file "modules.dep".

General Diagnostic

System resources

  • free - Show system memory availability and usage
  • df - Show the amount of disk free space on each mounted filesystem.
  • du - Show disk usage
  • lspci - List PCI devices
  • pnpdump - Lists ISA PNP device resource information.
  • vmstat - Reports virtual memory statistics.


  • env - List the current environment variables.
  • printenv - Print a copy of the environment.
  • set - Shows how the environment is set up. This command can be very useful when debugging the environment.
  • runlevel - List the current and previous runlevel.
  • uname - Print system information. In my case, it prints "Linux".
  • dmesg - Show the last kernel messages printed during the last boot.

Tools for working with processes

  • accton - Turns process accounting on and off. Uses the file /var/log/pacct. To turn it on type "accton /var/log/pacct". Use the command with no arguments to turn it off.
  • kill - Kill a process by number
  • killall - Send a signal to a process by name
  • lastcomm (1) - Display information about previous commands in reverse order. Works only if process accounting is on.
  • nice - Set process priority of new processes.
  • ps(1) - Used to report the status of one or more processes.
  • pstree(1) - Display the tree of running processes.
  • renice(8) - Can be used to change the process priority of a currently running process.
  • sa(8) - Generates a summary of information about users' processes that are stored in the /var/log/pacct file.
  • skill - Report process status.
  • snice - Report process status.
  • top - Displays the processes that are using the most CPU resources.

Unix / Linux shortcut keys

Shortcuts are designed to help shorten the time required to perform frequently used commands or actions. In the below sections I have listed keyboard shortcut keys that can be performed by pressing two or more keys at once. In addition to keyboard shortcut keys, I have also listed command line shortcut keys that can be typed in at the shell.

Please note that the below shortcut keys and command line shortcuts will not work on all variants of Unix and/or Linux.

Keyboard shortcut keys

  • CTRL + B Moves the cursor backward one character.
  • CTRL + C Cancels the currently running command.
  • CTRL + D Logs out of the current session.
  • CTRL + F Moves the cursor forward one character.
  • CTRL + H Erase one character. Similar to pressing backspace.
  • CTRL + P Paste previous line and/or lines.
  • CTRL + S Stops all output on screen (XOFF).
  • CTRL + Q Turns all output stopped on screen back on (XON).
  • CTRL + U Erases the complete line.
  • CTRL + W Deletes the last word typed in. For example, if you typed 'mv file1 file2' this shortcut would delete file2.
  • CTRL + Z Cancels current operation, moves back a directory and/or takes the current operation and moves it to the background. See bg command for additional information about background.

Command line shortcuts

In addition to the below command line shortcuts, it is also helpful to use the alias command that allows you to specify a keyword for frequently used commands or mistakes.

  • ~ Moves to the user's home directory.
  • !! Repeats the line last entered at the shell. See history command for previous commands.
  • !$ Repeats the last argument for the command last used. See history command for previous commands.
  • reset Resets the terminal if terminal screen is not displaying correctly.
  • shutdown -h now Remotely or locally shuts the system down.

Google funds Photoshop-on-Linux work

Google is funding work to ensure the Windows version of Adobe Systems' Photoshop and other Creative Suite software can run on Linux computers.

For the project, Google is funding programmers at CodeWeavers, a company whose open-source Wine software lets Windows software run on Linux. Wine is a compatibility layer that intercepts a program's Windows commands and converts them to instructions for the Linux kernel and its graphics subsystem.

"We hired
CodeWeavers to make Photoshop CS and CS2 work better under Wine," Dan Kegel, of Google's software engineering team and the Wine 1.0 release manager, said on Google's open-source blog. "Photoshop is one of those applications that desktop Linux users are constantly clamoring for, and we're happy to say they work pretty well now...We look forward to further improvements in this area."

Google already uses Wine for the Linux version of its Picasa software for editing, tagging, and uploading photos. Photoshop is a larger and more complicated package, however, not to mention updated to version CS3 for nearly a year, so it's likely the CodeWeavers programmers will have a lot of work on their hands.

A survey by desktop Linux advocate Novell found Photoshop is the top non-Linux application that Linux users would like to have. Although Adobe has dipped its toes into the desktop Linux waters, so far it hasn't made any major moves.

And with current technology trends, maybe Adobe never will see the need for Linux ports. With virtualization software from companies such as Parallels and VMware and improving support from chipmakers Advanced Micro Devices and Intel, it's getting easier to run multiple operating systems on the same computer.

Thursday, April 30, 2009

First Music Player that talks to you

The player speaks of its status. The new i-pod shuffle is all equipped with VoiceOver,2 the feature that gives iPod shuffle a voice. With the press of a button, it tells you what song is playing and who’s performing it. It can even tell you the names of your playlists, giving you a new way to navigate your music.

Feature List:
  • 1.8" tall by 0.3" thin to be exact.
  • VoiceOver.
  • Easy-access controls.
  • Multiple playlists.
  • Multi-music-lingual.
  • Fashion tech-cessory.
.... and much more.

Making and Managing Linux Filesystems

Programs used to manage filesystems

badblocks(8) - Search a device for badblocks. The command "badblocks /dev/hda" will search the first partition of the first IDE hard drive for badblocks.

cfdisk(8) - A partition table manipulator used to create or delete disk partitions.

dosfsck(8) - Used to check a msdos filesystem.

dumpe2fs(8) - Lists the superblock and blocks group information on the device listed. Use with a command like "dumpe2fs /dev/hda2". The filesystem on the device must be a Linux filesystem for this to work.

fdformat(8) - Performs s lowlevel format on a floppy disk. Ex: "fdformat /dev/fd0H1440".

fdisk(8) - Used to add or remove partitions on a disk device. It modifies the partition table entries.

fsck(8) - Used to check and/or repair a Linux filesystem. This should only be used on systems that are not mounted.

hdparm(8) - Used to get or set the hard disk parameters.

mkdosfs(8) - Used to create a msdos filesystem.

mke2fs(8) - Create a Linux native filesystem which is called a second extended filesystem. This creates the current version of the Linux filesystem.

mkfs(8) - Used to make a Linux filesystem on a device. The command "mkfs /dev/hdb1" will create a Linux filesystem on the first partition of the second IDE drive.

mkswap(8) - Creates a Linux swap area on a device.

mount(8) - Used to mount a filesystem. It supports many types of filesystems.

stat(1u) - Used to print out inode information on a file. Usage: stat filename

swapoff(8) - Used to de-activate a swap partition.

swapon(8) - Used to activate a swap partition.

tune2fs(8) - Used to adjust filesystem parameters that are tunable on a Linux second extended filesystem. The filesystem must not be mounted write when this operation is performed. Can adjust maximum mount counts between filesystem checks, the time between filesystem checks, the amount of reserved blocks, and other parameters.

umount(8) - Unmount a filesystem.

Making a Filesystem

Making a swap partition

"mkswap -c /dev/hda3 10336"

The -c has swap check for bad blocks. The 10336 is the size of the partition in blocks, about 10M. The system enables swap partitions at boot time, but if installing a new system you can type "swapon /dev/hda3" to enable it immediately.

Making an ext2 file system on a floppy

1. fdformat /dev/fd0H1440

2. mkfs -t ext2 -c /dev/fd0H1440

Other file systems:

A normal hard drive can have many types of filesystems on it. To create an ext2 file system, type "mke2fs -c /dev/hda2 82080" to create an 82 meg filesystem. Note: mkfs is a front end to many file system types including ext2, minux, and msdos.

Checking a Filesystem

fsck - Used to check and repair a filesystem.
fsck is a front end to a filesystem type specific fsck.ext2, fsck.minix, and fsck.msdos.

Syntax: fsck -t type device

Ex: fsck -t ext2 /dev/hda3

Friday, April 24, 2009

Upgrading to Ubuntu 9.04 From 8.10 (Desktop)

Here is the tutorial for upgrading Ubuntu 8.10 (Intrepid Ibex) desktop to latest Ubuntu Linux 9.04 (Jaunty Jackalope) over the Internet.

Ubuntu Linux support direct upgrade Ubuntu 9.04 from Ubuntu 8.10.

Make sure you have all updates applied to Ubuntu 8.10 before you start upgrade. To do this visit:
System -> Administration -> Update Manager

Ubuntu Update Manager

Click on "Install Updates"

Network Upgrade for Ubuntu Desktops over the Network

You can easily upgrade over the network as follows:

Visit System > Administration > Update Manager

Click the Check button to check for new updates.

A message will appear informing you of the availability of the new release.

Click Upgrade.

Follow the on-screen instructions.