Commands by arld101 (1)

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Schedule Nice Background Commands That Won't Die on Logout - Alternative to nohup and at
Check out the usage of 'trap', you may not have seen this one much. This command provides a way to schedule commands at certain times by running them after sleep finishes sleeping. In the example 'sleep 2h' sleeps for 2 hours. What is cool about this command is that it uses the 'trap' builtin bash command to remove the SIGHUP trap that normally exits all processes started by the shell upon logout. The 'trap 1' command then restores the normal SIGHUP behaviour. It also uses the 'nice -n 19' command which causes the sleep process to be run with minimal CPU. Further, it runs all the commands within the 2nd parentheses in the background. This is sweet cuz you can fire off as many of these as you want. Very helpful for shell scripts.

video volume boost

Insert a line at the top of a text file without sed or awk or bash loops
Yet another way to add a line at the top a of text file with the help of the tac command (reverse cat).

list block devices
Shows all block devices in a tree with descruptions of what they are.

Produce a pseudo random password with given length in base 64
Of course you will have to install Digest::SHA and perl before this will work :) Maximum length is 43 for SHA256. If you need more, use SHA512 or the hexadecimal form: sha256_hex()

Merge video files together using mencoder (part of mplayer)
Using mplayer's mencoder, you can merge video files together. '-oac' specifies the audio encoding (here copy, to just copy and not compress) '-ovc' specifies the video encoding (same thing).

Clean swap area after using a memory hogging application
When you run a memory intensive application (VirtualBox, large java application, etc) swap area is used as soon as memory becomes insufficient. After you close the program, the data in swap is not put back on memory and that decreases the responsiveness. Swapoff disables the swap area and forces system to put swap data be placed in memory. Since running without a swap area might be detrimental, swapon should be used to activate swap again. Both swapoff and swapon require root privileges.

Block all IPv4 addresses that has brute forcing our ssh server
For ipv6 use: grep -oE "\b([0-9A-Fa-f]{1,4}:){7}[0-9A-Fa-f]{1,4}\b"

MySQL dump restore with progress bar and ETA
Display a progress bar while restoring a MySQL dump.

To find the uptime of each process-id of particular service or process

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