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Avoid killing the X server with CTRL+C on the tty it was started from

Remove all unused kernels with apt-get
Remove old kernels (*-generic and *-generic-pae) via apt-get on debian/ubuntu based systems. Tested on ubuntu 10.04 - 12.04.

from the console, start a second X server
This starts a very basic X session, with just a simple xterm. You can use this xterm to launch your preferred distant session. $ ssh -X john@otherbox gnome-session Try also startkde or fluxbox or xfce4-session. To switch between your two X servers, use CTRL+ALT+F7 and CTRL+ALT+F8.

Monitor a file with tail with timestamps added

Determine MAC address of remote host when you know its IP address
arping sends ARP requests to a neighboring host. This won't work if there is an ARP subnet gateway in the middle. If there is, you'll just get the gateway's MAC address not the host's address you are really trying to get to.

Adding Prefix to File name
Good old bracket expansion :-) For large numbers of files, "rename" will spare you the for-loop, or the find/exec...

Convert CSV to JSON
Replace 'csv_file.csv' with your filename.

show hidden chars in vi

List the size (in human readable form) of all sub folders from the current location
Simple and easy to remember. -h is human, -d1 = depth 1. disk usage, human, depth 1

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"


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