I read a book about linux hardening (Hardening Linux by James Turnbull, 2005). The book suggests to remove the sync user. If I remove the sync user I am not able to call commands like
shutdown, because they are not found anymore.
I used the following command to remove the sync user:
userdel -r -f sync
The following error appears after I removed the user:
-bash: shutdown: command not found
why do these commands not work anymore? and is it possible to remove the sync user without any problem?