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====== Useful Linux Utilities ======


  * [[gpg]] options

===== Useful tools with hard to remember names =====

  * ''scrot -s'' -- takes screenshots of an area
  * generates passwords:
    - ''apg -a 1 -m 6 -x 6''
    - ''pwgen''
  * ''figlet foo'' -- creates an ASCII art formatted text



===== Mrxvt =====

[[http://materm.sourceforge.net/index.html|Mrxvt]] is a multitabbed terminal emulator based on RXVT. It doesn't require any heavy libraries like QT or GTK so it's ideal for a low powered laptop machine.

Place this into your ''~/.Xdefaults'' file for some nicer defaults.

<code>
mrxvt.font: 9x15
mrxvt.geometry: 100x30
mrxvt.reverseVideo: True
mrxvt.loginShell: True
mrxvt.scrollbarRight: True
mrxvt.scrollbarStyle: rxvt
mrxvt.bottomTabbar: True
mrxvt.saveLines: 1500
mrxvt.visualBell: True
Mrxvt.macro.Shift+Left: GotoTab -1
Mrxvt.macro.Shift+Right: GotoTab +1
</code>

Some tips:

  * Change tab with ''Shift+Right'' and ''Shift+Left''
  * Open a new tab with ''Shift+Ctrl+t''
  * Change the title of a tab by marking some text and middle click the tab's name
  * Open multiple tabs at startup with ''-tnum #'' in command-line args

===== SSH Port forwarding =====

Forward the webserver (port 127.0.0.1:80) at remote.host to your local machine (port 8080) and allow open this port (8080) on all local interfaces (-g):

  $> ssh user@remote.host -L 8080:127.0.0.1:80 -N -g

===== File Transfer through existing SSH connection =====

Have you ever been logged into a machine (maybe even over multiple hosts) and then needed a file from you local host on that machine? Using a second connection with scp is a pain in the a** especially with multiple hops. The solution is [[http://zssh.sourceforge.net/|zssh]] - a wrapper around SSH and the zmodem protocol.

On you local machine just install it (''apt-get install zssh'' is your friend) and probably add the following to your ''~/.bashrc''

  alias ssh=zssh

When you are on the remote machine just press ''CTRL-Space'' to go into interactive mode (very much like FTP). To send a file use this:

  sz -e <file>

The ''-e'' option works around non 8-Bit clean terminals. You only need the ''lrzsz'' and ''ssh'' packages installed on the remote machine.

===== vmstat =====

Gives you some info about memory stats, IO and CPU states. Give sample rate in seconds as parameter.

  #> vmstat 3

===== dig =====

This is a powerful replacement for ''nslookup''

Doing a zone transfer if allowed:

  $> dig @nameserver domain.tld axfr

===== Unlocking a CD Writer with cdrdao =====

If a write failes the writer stays inaccessable sometimes - giving an error like this:

  logical unit not ready, long write in progress

Resetting the SCSI or ATAPI bus doesn't help. The tool cdrdao has an option to reset the device properly:

  #> cdrdao unlock


<del>===== Copy an audio CD with cdrdao =====</del>
Will use the recorder for reading and writing:

  #> cdrdao copy --device 0,0,0 --driver generic-mmc --datafile /exchange/cd.img --eject

===== Burn an ISO Image with cdrecord =====

  #> cdrecord -v dev=0,0,0 speed=16 driveropts=burnfree image.iso

===== VIM Setup in source file =====

You can embed Setup Commands for VIM in the source file. Here is an example for a Shell Script:

  #Setup VIM: ex: et ts=2 nowrap syntax=sh :

===== pgrep and pkill =====

From the [[man>pgrep|manpage]]:

> pgrep  looks through the currently running processes and lists the process IDs which matches the selection criteria to stdout.  All the criteria have to match.  For example, ''pgrep -u root sshd'' will only list the processes called sshd AND owned by root.  On the other hand, ''pgrep -u root,daemon'' will list the processes owned by root OR daemon.
>
> pkill will send the specified signal (by default SIGTERM) to each process instead of listing them on stdout.

This is a nice replacement for constructions like ''%%kill `ps ax|grep 'foo'|grep -v 'grep'|awk '{print $1}'`%%''

===== nast =====

Sweet Network Analyzer (http://nast.berlios.de/) or just install the Debian Packages.

I like the ''-m'' (map LAN via ARP requests) and the ''-g'' (find a gateway host) switches most.


===== iostat I/O Device Usage Informations =====

This command-line tool is within the ''sysstat''-package and provides information about the cpu load/usage   and/or about basically any device in /dev/.
usage: iostat [device [device2..]] [refrehrate in sec] [repeats]
refrehsrate defaults to 0, means no repeats at all.
repeat defaults to infinite.


===== iptraf Network Load Informations =====

This command-line tool displays package information and Usage of several network interfaces.
It has a console-graphical interface and serveral configuration options. See man-page.

===== httrack Website Copier =====

To fetch a whole site use this command:

  $> httrack -K0 -%q0 --keep-alive --urlhack -D http://www.example.com

===== mplayer / mencoder =====

This gives you the suggested crop parameters:

  $> mplayer -vf cropdetect somemovie.avi


This concats two avi files

  $> cat part1.avi part2.avi| mencoder -noidx -ovc copy -oac copy -o output.avi -

For rotating MJPEG movies as produced by the [[PowerShot S2 IS]]. This is not completely lossless but the best way I could find:

  $> mencoder -vf rotate=2 -ovc lavc -lavcopts vcodec=mjpeg -oac copy -o output.avi input.avi