Здравствуйте. Делаю:
su - test
Password:
test@wks1198:~$ cp /bin/bash bash
test@wks1198:~$ cp /bin/zsh zsh
test@wks1198:~$ chmod u+s bash
test@wks1198:~$ chmod u+s zsh
bash-4.1$ whoami
pavel
bash-4.1$ /home/test/zsh
wks1198% whoami
test
Ожидаемо!
wks1198% exit
bash-4.1$ /home/test/bash
bash-4.1$ whoami
pavel
Почему?????
bash-4.1$ exit
exit
