Commands by keymon (18)

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Check variable has been set

Convert images (jpg, png, ...) into a PDF
Converts images (maybe from scans) into a PDF

Securely destroy data on given device hugely faster than /dev/urandom
This command generates a pseudo-random data stream using aes-256-ctr with a seed set by /dev/urandom. Redirect to a block device for secure data scrambling.

Extract audio stream from an video file using mencoder
This command extracts the audio stream of the video in $file and stores it in a file where the original suffix is changed to .mp3

Double your disk read performance in a single command
(WARN) This will absolutely not work on all systems, unless you're running large, high speed, hardware RAID arrays. For example, systems using Dell PERC 5/i SAS/SATA arrays. If you have a hardware RAID array, try it. It certainly wont hurt. You may be can test the speed disk with some large file in your system, before and after using this: $ time dd if=/tmp/disk.iso of=/dev/null bs=256k To know the value of block device parameter known as readahead. $ blockdev --getra /dev/sdb And set the a value 1024, 2048, 4096, 8192, and maybe 16384... it really depends on the number of hard disks, their speed, your RAID controller, etc. (see sample)

Simple way to envoke a secure vnc session through ssh enabled router.
The ip address is of the remote machine running the vncserver. Must log in first to the router then the VNC session. Very nice if you have open-wrt or dd-wrt on your router.

convert wav into mp3 using lame

Commit command to history file immedeately after execution
This could be added to .bashrc. Background: Linux usually saves history only on clean exit of shell. If shell ends unclean, history is lost. Also numerous terminals might confuse their history. With this variable set, history is immedeately written, accessible to all other open shells.

download the contents of a remote folder in the current local folder

send echo to socket network
this command will send a message to the socket 25 on host 192.168.1.2 in tcp. works on udp and icmp understand only IP address, not hostname. on the other side (192.168.1.2), you can listen to this socket and test if you receive the message. easy to diagnose a firewall problem or not.


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