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back ssh from firewalled hosts
host B (you) redirects a modem port (62220) to his local ssh. host A is a remote machine (the ones that issues the ssh cmd). once connected port 5497 is in listening mode on host B. host B just do a ssh 127.0.0.1 -p 5497 -l user and reaches the remote host'ssh. This can be used also for vnc and so on.

List your installed Firefox extensions

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"

Running a command at a specific time

diff the outputs of two programs
I've been looking for this for a long time. Does anybody know how to do this in dash (POSIX shell)? An alternative version might be: $ exiftool img_1.jpg | diff -

Remount root in read-write mode.
Saved my day, when my harddrive got stuck in read-only mode.

April Fools' Day Prank
Add this to a fiend's .bashrc. PROMPT_COMMAND will run just before a prompt is drawn. RANDOM will be between 0 and 32768; in this case, it'll run about 1/10th of the time. \033 is the escape character. I'll call it \e for short. \e7 -- save cursor position. \e[%d;%dH -- move cursor to absolute position \e[4%dm \e[m -- draw a random color at that point \e8 -- restore position.

Print diagram of user/groups
Parses /etc/group to "dot" format and pases it to "display" (imagemagick) to show a usefull diagram of users and groups (don't show empty groups).

Notepad in a browser (type this in the URL bar)
It doesn't save your notes, but it's great for jotting something down quickly.

Remove text from file1 which is in file2 and stores it in an other file
This command compares file2 with file1 and removes the lines that are in file1 from file2. Handy if you have a file where file1 was the origional and you want to remove the origional data from your file2.


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