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Add an iptables rule on RH/CentOs before the reject
Rather then editing the /etc/sysconfig/iptables file, or during a kickstart doing some awk/sed magic, easily add a rule in the correct place within iptables

list files recursively by size

Get the time from NIST.GOV
The format is JJJJJ YR-MO-DA HH:MM:SS TT L DUT1 msADV UTC(NIST) OTM and is explained more fully here: http://tf.nist.gov/service/acts.htm

Create md5sum of files under the current dir excluding some directories
Useful if you want get all the md5sum of files but you want exclude some directories. If your list of files is short you can make in one command as follow: $ find . -type d \( -name DIR1 -o -name DIR2 \) -prune -o -type f -exec md5sum {} \; Alternatively you can specify a different command to be executed on the resulting files.

Find unused IPs on a given subnet

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

Prints per-line contribution per author for a GIT repository
Uses line-porcelain in git blame, which makes it easier to parse the output.

Swap a file or dir with quick resotre
This lets you replace a file or directory and quickly revert if something goes wrong. For example, the current version of a website's files are in public_html. Put a new version of the site in public_html~ and execute the command. The names are swapped. If anything goes wrong, execute it again (up arrow or !!).

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"

Fastest Sort. Sort Faster, Max Speed
sort is way slow by default. This tells sort to use a buffer equal to half of the available free memory. It also will use multiple process for the sort equal to the number of cpus on your machine (if greater than 1). For me, it is magnitudes faster. If you put this in your bash_profile or startup file, it will be set correctly when bash is started. $ sort -S1 --parallel=2 /dev/null && alias sortfast='sort -S$(($(sed '\''/MemF/!d;s/[^0-9]*//g'\'' /proc/meminfo)/2048)) $([ `nproc` -gt 1 ]&&echo -n --parallel=`nproc`)' Alternative $ echo|sort -S10M --parallel=2 &>/dev/null && alias sortfast="command sort -S$(($(sed '/MemT/!d;s/[^0-9]*//g' /proc/meminfo)/1024-200)) --parallel=$(($(command grep -c ^proc /proc/cpuinfo)*2))"


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