This is useful if you add sid, install some packages, then remove sid and want to work out which packages you installed from sid that should be removed (e.g. before an upgrade to the new stable). Alternatively you can think of this as "find installed packages that can no longer be installed."

Use lsbk (list block) and jq (to manipulate a JSON on the command line) to display partition information: Show Sample Output

It repeats a command, such as free, every five seconds and highlights the differences

Sometimes things break. You can find the most recent errors using a combination of journalctl, along with the classic tools sort and uniq Show Sample Output

Raise your hand if you haven't used this at least once to share a directory quickly

The shell {} operator is great for this. Here's an example with three directories enclosed in {}:

https://wuseman.nr1.nu:8080/file/E8AcLVgMPZ2LSJQf/9BD8V8ADYNhR6cca/parallel_print_progress.gif Show Sample Output

Should run anywhere that Bash works.. Your mileage may vary. Show Sample Output

After downloading an ISO image, assuming you have QEMU installed, it’s possible to boot an ISO image in a virtual machine and then install that ISO from within the virtual machine directly to a physical drive, bypassing the need to reboot. Simply pass the ISO image as the -cdrom parameter, followed by “format=raw,file=/dev/sdb” (replace /dev/sdb with the drive you want to install to) as the hard drive parameter (making absolutely certain to specify the raw format, of course). Once you boot into the ISO image with QEMU, just run the installer as if it were a virtual machine — it’ll just use the physical device as an install target. After that, you’ll be able to seamlessly boot multiple distros (or even other operating systems) at once.

Lists all installed kernels minus the current one. This is useful to uninstall older kernels that take too much space on /boot partition. Show Sample Output

This is a very hackish way to do it that I'm mainly just posting for fun, and I guess technically can more accurately be said to result in undefined behavior. What the command does is tell the shell to treat libpng like it's a shell plugin (which it's most certainly not) and attempt to install a "png_create_read" command from the library. It looks for the struct with the information about the command; since it's always the command name followed by "_struct", it'll look for a symbol called "png_create_read_struct". And it finds it, since this is the name of one of libpng's functions. But bash has no way to tell it's a function instead of a struct, so it goes ahead and parses the function's code as if it was command metadata. Inevitably, bash will attempt to dereference an invalid pointer or whatever, resulting in a segfault.

Useful when you wait for a server to boot up.

Since systemd-resolved was implemented, add a DNS server have become weirder and harder than before. With this command, you can add a DNS server on-the-fly tied to an specific interface

Check if TCP port is reacheable Show Sample Output

Clear Cached Memory on Ubuntu based distributions, and also display memory status. Please do not use this on a production machine unless you really really know what you are doing. Echo 3 is a kinder way of purging the memory, you can also use 'echo 2' or 'echo 1' if #1 You know what you are doing, and #2 refer to number 1 :-)

Useful for checking if a large number of PNG files was downloaded successfully by verifying the built-in CRC checksum. For incomplete files, the command will print: "00002309.png EOF while reading IDAT data ERROR: 00002309.png" The process is very fast; checking 21,000 files of 5MB in size took only five minutes on a 2011 Intel mobile dual-core.

Read a file or standard input and only outputs lines that start with a dot or period "." Show Sample Output

Directly download all mp3 files of the desired podcast

This command will take the output of a command and color any STDERR output as a different color (red outline in this case) Show Sample Output