user at miner in ~
$ cat /etc/shells
# /etc/shells: valid login shells
/bin/sh
/bin/dash
/bin/bash
/bin/rbash
/usr/bin/tmux
/usr/bin/screen
/usr/bin/fish
user at miner in ~
$ ls /usr/bin/fish
/usr/bin/fish*
user at miner in ~
$ ll /usr/bin/fish
-rwxr-xr-x 1 root root 817K May 15 09:15 /usr/bin/fish*
user at miner in ~
$ chsh -s /usr/bin/fish
You may not change the shell for 'user'.
user at miner in ~
$ sudo chsh -s /usr/bin/fish
Password:
chsh: PAM authentication failed
user at miner in ~
$ sudo chsh -s /usr/bin/fish user
Password:
chsh: PAM authentication failed
user at miner in ~
$ u
fish: Unknown command “u”
u: command not found
user at miner in ~
$ whoami
user