The file myfile is owned by tom and has read and write permissions for tom. Group and other permissions are empty which make myfile readable and writable only by tom. setfacl enables user tom to give read permission to user john only. The command 'ls -l' shows a '+' sign telling us that file access control list has been setup for myfile.

works like a charm for the K610i

greps for search word in directory and below (defaults to cd).

-i case insensitive

-n shows line number

-H shows file name

I often need to send screenshots to other people to explain settings and whatever.

So I created this oneline which I use to create the screenshot with imagemagik, upload it via scp to my server and then the command opens an firefox tab with the screenshot.

The screenshot can be a region or a window.

You just have to replace the parts beginning with YOUR.

Good for automating reports that need to run from between two dates.

the -A argument forwards your ssh private keys to the host you're going to. Useful in some scenarios where you have to hop to one server, and then login to another using a private key.

kills all pids matching the search term of "PROCESS". Be careful what you wish for :)

queries local memcached for stats, calculates hit/get ratio and prints it out.

Ran as the postgres user, dumps each database individually. It dumps with the create statements as well, so you can just 'zcat $x-nightly.dmp.gz | psql' to reimport/recreate a database from a backup.

Find files that are older than x days in the working directory and list them. This will recurse all the sub-directories inside the working directory.

By changing the value for -mtime, you can adjust the time and by replacing the ls command with, say, rm, you can remove those files if you wish to.

mtr combines the functionality of the traceroute and ping programs in a single network diagnostic tool.

As mtr starts, it investigates the network connection between the host mtr runs on and HOSTNAME. by sending packets with purposly low TTLs. It continues to send packets with low TTL, noting the response time of the intervening routers. This allows mtr to print the response percentage and response times of the internet route to HOSTNAME. A sudden increase in packetloss or response time is often an indication of a bad (or simply over‐loaded) link.

Note that the file at the given path will have the contents of the (still) deleted file, but it is a new file with a new node number; in other words, this restores the data, but it does not actually "undelete" the old file.

I posted a function declaration encapsulating this functionality to http://www.reddit.com/r/programming/comments/7yx6f/how_to_undelete_any_open_deleted_file_in_linux/c07sqwe (please excuse the crap formatting).

This runs a command continuously, restarting it if it exits. Sort of a poor man's daemontools. Useful for running servers from the command line instead of inittab.

An easy way to create aliases for moving between many directories

Long before tabbed terminals existed, people have been using Gnu screen to open many shells in a single text terminal. Combined with ssh, it gives you the ability to have many open shells with a single remote connection using the above options. If you detach with "Ctrl-a d" or if the ssh session is accidentally terminated, all processes running in your remote shells remain undisturbed, ready for you to reconnect. Other useful screen commands are "Ctrl-a c" (open new shell) and "Ctrl-a a" (alternate between shells). Read this quick reference for more screen commands: http://aperiodic.net/screen/quick_reference

I often need to add a timestamp to a file, but I never seem to remember the exact format string that has to be passed to the date command to get a compact datetime string like 20090220T231410 (i.e yyyymmddThhmmss, the ISO 8601 format popular outside the US)

mplayer -vo caca will give you a similar result but in color