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I installed fishfish(a user-friendly interactive command line shell) on a Linux server, later somebody uninstalled it but I don't know it. After I run chsh -s /usr/local/bin/fish without caution, I cannot login the server now. Error message "login: no shell: No such file or directory" showed up which apparently says that shell fish do not exist anymore.

The server provides only a CLI interface, so how can I change the login shell when I cannot even login?

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Do you have access to a root account? –  rahmu Jun 8 '12 at 8:48
    
@rahmu I ran chsh under account root. I changed root's shell. –  xanpeng Jun 8 '12 at 9:14
    
@xanpeng You did it wrong, its chsh username_to_change from the root account. –  Tim Jun 8 '12 at 13:57
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And this would be why you should ALWAYS set the root account's shell to something basic that never gets undeleted, like sh or bash. –  Shadur Jun 8 '12 at 14:20
    
@Shadur Yes, I did it wrong, lesson learned: should be more careful when you are root. –  xanpeng Jun 8 '12 at 15:20

1 Answer 1

If you have access to the root account, you can change the shell for a user from there using chsh -u user -s $SHELL.

If you have access to the boot process, you can append init=$SHELL to be dropped to a single-user shell, where you can fix this, again with chsh -u user -s $SHELL (some systems using a two-stage boot with an initrd image may require you to use real_init instead). You will probably need to remount the filesystem containing /etc/passwd as read-write (using mount -o remount,rw / or similar).

Otherwise, if you can su into the user from another user, try su user -c $SHELL, or if you can ssh into the user, you could try something like ssh user@localhost $SHELL.

You could also boot into a live CD/USB, mount / and fix /etc/passwd manually.

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Thanks. (1) As I changed login shell for root himself, so I guess method #1 cannot work. (2) For method #2 "change boot process", I'm wondering how to remount the filesystem? I'm out of the shell, I cannot execute mount. I tried init=/bin/bash and `real_init=/bin/bash, neither of them worked. (3) For method #3, it cannot work as we have only one account, root, in the server OS. –  xanpeng Jun 8 '12 at 10:01
    
@xanpeng I gave the command to remount the root filesystem (which is probably where you have /etc). You should be able to SSH in from another machine. –  Chris Down Jun 8 '12 at 10:52

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