coreutils

cut

cut -d "," -f 1 filename

... displays only the first field for each line in filename, using "," as a delimiter

date

date -s '2014-12-25 12:34:56'

... set the current date / time ISO style

date --set='+2 minutes'

... set the current date (time)

date -d @1190000000

... displays UNIX / epoch time 1190000000 as local time.

date +%s -d"Jan 1, 1980 00:00:01"

... displays "Jan 1, 1980 00:00:01" as UNIX /epoch time

dd

dd if=/dev/sdX of=/home/user/mbr.img bs=446 count=1

... backups the MBR record of /dev/sdX to /home/user/mbr.img

dd if=/dev/zero of=/dev/sdX bs=446 count=1

... removes the MBR record from /dev/sdX

dd if=/home/user/mbr.img of=/dev/sdx bs=446 count=1

... restores the MBR record for /dev/sdX from /home/user/mbr.img

dd if=/dev/zero of=myimage.img bs=1m count=512

... create an empty 512MB image

Using dd on specific images

dd if=FreeBSD-XXXX-RELEASE-amd64-memstick.img of=/dev/da0 bs=1M conv=sync

... FreeBSD

dd if=install-amd64-minimal-XXX.iso of=/dev/sdX bs=4096 status=progress && sync

... Gentoo

dd if=/path/to/systemrescue.iso of=/dev/sdX status=progress

... SystemRescue