What happens when you chsh without a user name?

AturSams

1/17/24, 4:44 AM

One may: sudo chsh -s /bin/sh or sudo chsh -s /bin/sh user_name

It is understood that the second command changes the shell for the specified user_name but unclear what happens without specifying a user_name and where is that reflected?

Thank you!

437

1 + 0

chsh

Score:6

Ubuntu

Terrance

1/17/24, 4:58 AM

The command without a user changes the root user:

terrance@terrance-ubuntu:~$ sudo chsh -s /bin/sh
terrance@terrance-ubuntu:~$ cat /etc/passwd | grep "/bin/sh"
root:x:0:0:root:/root:/bin/sh
terrance@terrance-ubuntu:~$ sudo chsh -s /bin/bash
terrance@terrance-ubuntu:~$ cat /etc/passwd | grep "/bin/bash"
root:x:0:0:root:/root:/bin/bash

+ 6

AturSams

1/17/24, 8:12 AM

So it is essentially like typing `sudo chsh -s /bin/bash root` ?

Terrance

1/17/24, 1:00 PM

@AturSams Correct, it is the same as that. To run the command on your own user, sudo is not needed and neither is your username.

Simon Richter

1/17/24, 1:36 PM

Specifically, using `sudo` is a bad idea: normal users are limited to shells listed in `/etc/shells`, so users cannot accidentally lock themselves out by switching to something that isn't a working shell. As root, you can set anything, including something that doesn't work.

Simon Richter

1/17/24, 1:37 PM

The reason `sudo chsh` changes the shell for root is that `sudo` switches to root, and `chsh` changes the shell of the current user.

AturSams

1/17/24, 3:42 PM

@SimonRichter Thanks for clarifying. :)

Joshua

1/17/24, 7:32 PM

Which makes quite a bit of sense; `chsh` without `sudo` would change the user's own shell. I'm kind of disappointed that on too many linux systems, `chsh` without `sudo` yields an error.

Elon Musk

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EN: What happens when you chsh without a user name?

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