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My web server was tampered by someone who was using zsh shell. I feel more comfortable using bash shell, as that's the defaults that come with Ubuntu and OS X (the two main operating systems I use). But this questions is focused on Ubuntu server.

I have 4 websites running on this web server, I use byobu, I use tmux, I use ruby/ruby on rails, node.js, Apache, a few daemons. If I switch the current root shell from zsh to bash, could there be any negative side effects that might result from this switch? For example, will processes be killed because their parent process (the shell) has been switched?

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  • Are you asking about the consequences of the change (which are none, I'm using zsh right now and can switch to bash whenever I like) or are you asking about how to effectively change the shell?
    – Braiam
    Dec 3, 2013 at 23:59
  • @Braiam I am nervous about the consequences of the change. If there are no consequences, then I will change. I was just thinking that the shell was a parent process to some of these daemons like apache, and if I was to switch out of it, that it would kill the apache process. But I guess I am wrong. Dec 4, 2013 at 0:03

4 Answers 4

37

Answer from the Stack Overflow (switching from zsh to bash):

You can just use exec to replace your current shell with a new shell:

Switch to bash:

exec bash

Switch to zsh:

exec zsh

This won't affect new terminal windows or anything, but it's convenient.

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  • 1
    did not work. still : echo $SHELL /usr/bin/zsh
    – ses
    Sep 29, 2017 at 1:38
  • @ses $SHELL gives you the default login shell. $0 gives you the current shell (the name of the running process) and $$ is the process ID (PID) of the script itself. Try ps $$ or echo $0 Jan 2, 2021 at 4:46
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Changing your shell, via sudo chsh --shell=/bin/bash $USER will change the shell field in /etc/passwd. This value is only consulted at login time, when the system has no idea of which shell to use for you.

Running processes, whether started by zsh, bash apache or evil_overlord's_program won't be affected

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  • Isn't the shell the parent process of other processes running in it, or just the controlling terminal (and not the shell) would be considered the parent process? Mar 13, 2014 at 19:50
  • The login program runs in a process, like everything. When it lets you in, it creates another process with your UID, etc, and runs /bin/bash (from /etc/passwd). The bash shell reads from STDIN (set up by login), and will fork/exec non-builtin commands, wait for them to terminate, and loop for more commands. The idea of "controlling terminal" is not useful in Unix/Linux.
    – waltinator
    Mar 13, 2014 at 23:49
9

Open your terminal and use the following command:

chsh -s $(which bash)
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  • I assume this is the equivalent of chsh -s /bin/bash Mar 13, 2014 at 19:45
  • 2
    which bash would give the absolute path of bash, so it would be the same if /bin/bash is where bash was located. Jan 28, 2015 at 8:42
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On Mac OS Catalina

  1. Change to zsh:

    chsh -s /bin/zsh
    
  2. Change to bash:

    chsh -s /bin/bash
    

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