2

I connect to a server via ssh.

Now i wanted to set the shell to bash, because at the moment the shell is sh.

sudo /sbin/usermod -s /usr/bin/bash santi

Should i use /bin/bash or /usr/bin/bash or does it not matter?

Marcus Müller
  • 28,836
Santiago
  • 215
  • 4
    Does Bash exist as /bin/bash? or as /usr/bin/bash? or in both places? If in both places, is it the same Bash? Is /bin symlinked to usr/bin maybe? – Kamil Maciorowski May 04 '23 at 10:00
  • 1
    When i ls -la i see bash in both, in /bin and in /usr/bin, i can set both path with usermod. how can i find out if this a symlinked and and what does that matter? – Santiago May 04 '23 at 10:08
  • You didn't say which system you're running, but at least if it's a recent-ish Linux distribution, these might be relevant https://askubuntu.com/questions/1242157/why-are-bin-and-sbin-now-symlinks-in-ubuntu-20-04 https://wiki.debian.org/UsrMerge https://lwn.net/Articles/483921/ – ilkkachu May 04 '23 at 10:27

4 Answers4

8

The permitted shells are listed in the file /etc/shells.

Run the chsh from the santi account, without sudo. It will prevent you from using a non-permitted shell.

The administrator can set a non-permitted shell, but that's a bad idea unless you're deliberately setting up a user account with restricted access. One reason is that ordinary users can't change it anymore. Another reason is that distributions keep /etc/shells updated, so an upgrade won't prevent users from logging in, but if you use administrator powers to give an account a non-permitted shell, then the burden is on you to be careful not to lock that account out.

Gilles 'SO- stop being evil'
  • 829,060
  • Software like ftpd treats users differently depending on whether their login shell is in /etc/shells. – Barmar May 05 '23 at 14:31
5

For determine what is the path of the bash executable on your system, you can use the following command:

command -v bash

You can list available shells on your system too:

cat /etc/shells

If you want an interactive way to set the shell:

chsh <userame>

Hope this helps !

ramius
  • 853
4

If bash is available both in /bin/bash and /usr/bin/bash (typically because /bin is a symlink to /usr/bin due to the /usr merge) it does not matter. Both will work on this system

I would however prefer to use /bin/bash over /usr/bin/bash, as that's the traditional location where it was installed, and it would be more compatible if run in other systems (if instead of being a manual step this was included on a script that might be run on multiple machines, or if the location of bash was for writing it on a shebang)

Ángel
  • 3,589
3

One of them is probably a link to the other...

Traditionally, shells (like bash, csh and zsh) are located in /bin - because a shell is needed even in single user mode or other times when /usr may be unmounted (/usr is often on a separate partition and may even be mounted through the network - thus not readily available in singe user mode).

On the other hand, additional shells (than the default one/ones) aren't strictly needed in single user mode (unless root happens to use one of them), so it's natural to put such shells it in /usr/bin instead of /bin.

what's the difference between /bin/zsh and /usr/bin/zsh?

Both /bin/bash and /usr/bin/bash are valid paths for the Bash shell executable.

The difference between /bin/bash and /usr/bin/bash is historical and depends on the system conventions and configuration.

Traditionally, Bash was installed in the /bin path on Unix systems, some modern Linux distributions store it in the /usr/bin path. Most system create symbolic link from /bin/bash to /usr/bin/bash, which means that both paths are equivalent.

/usr/bin is the default location for user-level executables on most modern Linux distributions. This path contains user-installed executables and is typically not mounted until later in the boot process.

/usr/bin/bash is the path to the bash executable if it is installed in this location.

The symbolic link ensures that legacy scripts and applications that reference /bin/bash will continue to work correctly even if the Bash executable is installed in /usr/bin

You can use /bin/bash or /usr/bin/bash in the usermod command to set the shell for the user santi

Both will work correctly.

zsh is in /usr/bin, but also in /bin, what is the difference?

Differences between /bin, /sbin, /usr/bin, /usr/sbin, /usr/local/bin, /usr/local/sbin

Filesystem Hierarchy Standard

Difference between /bin/bash and /usr/bin/bash

What is the difference if I start bash with "/bin/bash" or "/usr/bin/env bash"?

Z0OM
  • 3,149