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Mapreduce style processing
parallel can be installed on your central node and can be used to run a command multiple times. In this example, multiple ssh connections are used to run commands. (-j is the number of jobs to run at the same time). The result can then be piped to commands to perform the "reduce" stage. (sort then uniq in this example). This example assumes "keyless ssh login" has been set up between the central node and all machines in the cluster. bashreduce may also do what you want.

Check if network cable is plugged in and working correctly
with 'mii-tool -w eth0' you can watch the interface for changes of the link status

Remove blank lines from a file using grep and save output to new file

complete extraction of a debian-package
extracts the debian-package $debfile to $extractdir, including all packaging-information. to repack the package, just type: $dpkg-deb -b $extractdir

Compare a remote dir with a local dir
You can compare directories on two different remote hosts as well: $ diff -y

Check if port is open on remote machine
Check if port is open, if you don't have ncat on your machine.

Create a directory and go inside it
$_ expands to the last argument of the last command that was executed

Advanced python tracing
Trace python statement execution and syscalls invoked during that simultaneously

Given a file path, unplug the USB device on which the file is located (the file must be on an USB device !)
You have an external USB drive or key. Apply this command (using the file path of anything on your device) and it will simulate the unplug of this device. If you just want the port, just type : echo $(sudo lshw -businfo | grep -B 1 -m 1 $(df "/path/to/file" | tail -1 | awk '{print $1}' | cut -c 6-8) | head -n 1 | awk '{print $1}' | cut -c 5- | tr ":" "-")

A "Web 2.0" domain name generator and look for register availability
You would need pwgen installed first, on ubuntu you can get it by apt-get $ sudo apt-get install pwgen


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