Possible side effects of changing shell from zsh to bash

Question

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?

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 03 '13 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. — JohnMerlino, Dec 04 '13 at 00:03

score 37 · Answer 1 · edited May 23 '17 at 12:39

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.

edited May 23 '17 at 12:39

Community

1

answered Jun 22 '15 at 01:54

Swap

499

1

did not work. still : echo $SHELL /usr/bin/zsh – ses Sep 29 '17 at 01:38
@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 – Pablo Bianchi Jan 02 '21 at 04:46

score 12 · Accepted Answer · answered Dec 04 '13 at 01:11

12

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

answered Dec 04 '13 at 01:11

waltinator

36,399

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? – JohnMerlino Mar 13 '14 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 '14 at 23:49

score 9 · Answer 3 · edited Dec 04 '13 at 08:44

9

Open your terminal and use the following command:

chsh -s $(which bash)

edited Dec 04 '13 at 08:44

Radu Rădeanu

169,590

answered Dec 04 '13 at 05:29

Raja G

102,391
106
255
328

I assume this is the equivalent of chsh -s /bin/bash – JohnMerlino Mar 13 '14 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. – ryanjdillon Jan 28 '15 at 08:42

score 2 · Answer 4 · answered Jun 11 '19 at 03:39

2

On Mac OS Catalina

Change to zsh:
```
chsh -s /bin/zsh
```
Change to bash:
```
chsh -s /bin/bash
```

answered Jun 11 '19 at 03:39

Mono

21

Possible side effects of changing shell from zsh to bash

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