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dd if=/dev/null of=/dev/sda
removes all files/filesystems of a harddisk. It removes EVERYTHING of your hard disk. Be carefull when to select a device. It does not prompt for and second check.

ncdu - ncurses disk usage
ncdu is a text-mode ncurses-based disk usage analyzer. Useful for when you want to see where all your space is going. For a single flat directory it isn't more elaborate than an du|sort or some such thing, but this analyzes all directories below the one you specify so space consumed by files inside subdirectories is taken into account. This way you get the full picture. Features: file deletion, file size or size on disk and refresh as contents change. Homepage: http://dev.yorhel.nl/ncdu

Update IP filter for qBittorrent
Downloads Bluetack's level 1 IP blocklist in .p2p format, suitable for various Bittorrent clients.

Detect illegal access to kernel space, potentially useful for Meltdown detection
Based on capsule8 agent examples, not rigorously tested

See system users

DVD ripping with ffmpeg
To rip DVD movie to ogg format using ffmpeg, follow these steps. 1) find the vob files on the mounted video DVD in VIDEO_TS that stores the movie itself. There would be a few other VOB files that stores splash screen or special features, the vob files for the movie itself can be identified by its superior size. You can verify these vob files by playing them directly with a player (e.g. mplayer) 2) concatenate all such vob files, pipe to ffmpeg 3) calculate the video size and crop size. The ogg video size must be multiple of 16 on both width and height, this is inherit limitation of theora codec. In my case I took 512x384. The -vcodec parameter is necessary because ffmpeg doesn't support theora by itself. -acodec is necessary otherwise ffmpeg uses flac by default.

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"

Rename files in batch

Copy a file and force owner/group/mode
This is useful when you want to copy a file and also force a user, a group and a mode for that file. Note: if you want to move that file instead of copying it, you can use $install -o user -g group -m 755 /path/to/file /path/to/dir/ && rm -f /path/to/file which will remove the file only if the install command went fine.

Equivalent to ifconfig -a in HPUX


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