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Number of CPU's in a system
this works for a Linux based system, other UNIX systems may have other way(s) to check the number of CPUs.

To find the count of each open file on a system (that supports losf)

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"

generate a randome 10 character password

Undo commit in Mercurial

Create a CD/DVD ISO image from disk.
Many like to use 'dd' for creating CD/DVD iso images. This is bad. Very bad. The reason this is, is 'dd' doesn't have any built-in error checking. So, you don't know if you got all the bits or not. As such, it is not the right tool for the job. Instead, 'reaom' (read optical media) from the wodim package is what you should be using. It has built-in error checking. Similarly, if you want to burn your newly creating ISO, stay away from 'dd', and use: $ wodim -v -eject /path/to/image.iso

How to run X without any graphics hardware
This starts an X server using Xvfb(1) (no graphics hardware required), then starts a VNC server on the display. Change :1 if there's a conflict with an existing display, and change 800x600x24 to suit your tastes (24 is the bit depth, 800x600 is the size). This command obviously requires X be installed, and also x11vnc(1); both are available via your favourite package manager. You can also use another VNC server of your choosing, as long as DISPLAY is set to the display of Xvfb(1). To change your desktop environment (the default is twm(1), which is rather fail), you can add it to your ~/.xinitrc file (see the startx(1) manpage for details).

Retrieve the size of a file on a server
- Where $URL is the URL of the file. - Replace the $2 by $3 at the end to get a human-readable size. Credits to svanberg @ ArchLinux forums for original idea. Edit: Replaced command with better version by FRUiT. (removed unnecessary grep)

copy public key

Find Out My Linux Distribution Name and Version


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