First or last symbols in string

Last 12 symbols from UUID:

uuidgen | tail -c 12

First 8 symbols from UUID:

uuidgen | head -c 8

Add user to group

sudo usermod -aG $GROUP $USER

Linux rescue

In grub menu select autoline and press e. Find the line which is started with linux and append


to the end of this. After you will boot it (Ctrl-x), you will get a root shell immediately. But the filesystme will be in the readonly mode. To fix it execute:

mount -o remount, rw /