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Remove invalid host keys from ~/.ssh/known_hosts
Useful if you have to tunnel ssh through a local port and it complains of the host key being different. Much easier than manually editing the file.

Monitoring file handles used by a particular process
-r : repeat mode

matrix in your term
-a : Asynchronous scroll -b : Bold characters on -x : X window mode, use if your xterm is using mtx.pcf

search the manual page names and descriptions

Top 20 commands in your bash history

Transfer a file to multiple hosts over ssh
You can push files to up to 32 servers at once assuming ssh keys are in place. Great tool, it is part of the pssh suite.

Download entire commandlinefu archive to single file
'jot' does not come with most *nix distros, so we need to use seq to make it work. This version tested good on Fedora 11.

Delete specific sender in mailq

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Destroy all disks on system simultaneously
This command will use the fdisk utility to find all block devices on your system, and overwrite them with data from the /dev/urandom non-blocking random number generator. CAUTION: This will irrevocably erase EVERY SINGLE physical block storage device visible to the fdisk utility, including plugged USB devices, RAID sets, LVM, etc.


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