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Realtime lines per second in a log file
Using tail to follow and standard perl to count and print the lps when lines are written to the logfile.

Synchronize both your system clock and hardware clock and calculate/adjust time drift
Do not run this command if you already have ntpd running! This needs to run as root, for example with sudo: $ sudo ntpdate pool.ntp.org && sudo hwclock --systohc && sudo hwclock --adjust This command will fetch accurate time from NTP servers and synchronize your system clock, then it will use the system clock to synchronize your hardware clock, and will calculate the time drift.

Get ssh server fingerprints
Get your server's fingerprints to give to users to verify when they ssh in. Publickey locations may vary by distro. Fingerprints should be provided out-of-band.

A DESTRUCTIVE command to render a drive unbootable
Overwrites the boot sector. Since this doesn't overwrite any data, you can usually recover by re-creating the partition table exactly the same as before you zeroed it. This can also help sometimes if you install a new drive in a Windows machine which can't read it.

Print just line 4 from a textfile

List only directories, one per line
Alternatively, $ ls -F | grep /\$ but will break on directories containing newlines. Or the safe, POSIX sh way (but will miss dotfiles): $ for i in *; do test -d "./$i" && printf "%s\n" "$i"; done

Send an http HEAD request w/curl

Empty the linux buffer cache

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

Copy a file with progress and save hash to a different file


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