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Copy files and directories from a remote machine to the local machine
This command will copy files and directories from a remote machine to the local one. Ensure you are in the local directory you want to populate with the remote files before running the command. To copy a directory and it's contents, you could: $ ssh user@host "(cd /path/to/a/directory ; tar cvf - ./targetdir)" | tar xvf - This is especially useful on *nix'es that don't have 'scp' installed by default.

Install pip with Proxy
Installs pip packages defining a proxy

Find usb device in realtime
Using this command you can track a moment when usb device was attached.

Find the package a command belongs to on debian-based distros
Advanced revision to the command 8776 . This revision follows symbolic links. The quotation-marks surrounding $(which $1) allows for graceful handling of errors ( ie. readlink does not complain incase 'which' command generates (null) output)

Disable annoying sound emanations from the PC speaker
To ensure that it will never come back, you can edit /etc/modprobe.d/blacklist Add "blacklist pcspkr" sans quotes

ssh and attach to a screen in one line.
If you know the benefits of screen, then this might come in handy for you. Instead of ssh'ing into a machine and then running a screen command, this can all be done on one line instead. Just have the person on the machine your ssh'ing into run something like $ screen -S debug Then you would run $ ssh -t user@host screen -x debug and be attached to the same screen session.

Repoint an existing symlink to a new location
Instead of deleting an existing symlink and then re-creating it pointing at the new location, it is possible to perform the same action with this one command. Interesting discussion on whether this is possible to do atomically here: http://answers.google.com/answers/threadview?id=526119

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Rsync using SSH and outputing results to a text file
--delete will delete copies on remote to match local if deleted on local --stats will output the results -z zip -a archive -A preserve ACL -x don't cross filesystem boundaries -h human readable -e specify the remote shell to use

Check for login failures and summarize
This command checks for the number of times when someone has tried to login to your server and failed. If there are a lot, then that user is being targeted on your system and you might want to make sure that user either has remote logins disabled, or has a strong password, or both. If your output has an "invalid" line, it is a summary of all logins from users that don't exist on your system.


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