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Port Knocking!
Knock on ports to open a port to a service (ssh for example) and knock again to close the port. You have to install knockd. See example config file below. [options] logfile = /var/log/knockd.log [openSSH] sequence = 3000,4000,5000 seq_timeout = 5 command = /sbin/iptables -A INPUT -i eth0 -s %IP% -p tcp --dport 22 -j ACCEPT tcpflags = syn [closeSSH] sequence = 5000,4000,3000 seq_timeout = 5 command = /sbin/iptables -D INPUT -i eth0 -s %IP% -p tcp --dport 22 -j ACCEPT tcpflags = syn

Backup all databases in a MySQL container

GRUB2: Set Imperial Death March as startup tune
Kudos to http://www.commandlinefu.com/commands/view/8275/grub2-set-super-mario-as-startup-tune

Keep from having to adjust your volume constantly
Run this in the directory you store your music in. mp3gain and vorbisgain applies the ReplayGain normalization routine to mp3 and ogg files (respectively) in a reversible way. ReplayGain uses psychoacoustic analysis to make all files sound about the same loudness, so you don't get knocked out of your chair by loud songs after cranking up the volume on quieter ones.

Synchronize date and time with a server over ssh
Set Remote Server Date using Local Server Time (push)

Command line calculator
This opens a python command line. You can use math and random and float-division is enabled (without appending .0 to integers). I just don't know how to specify a standard precision.

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Aptitude pattern match
Could be dangerous, if you have many packages all beginning with 'foo' or 'bar'. This will easily remove them all from your system.

add repeated watermark to image

Search for commands from the command line
Search at CommandLineFu.com from your terminal. Get the clfu-seach at http://www.colivre.coop.br/Aurium/CLFUSearch


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