Ability to run bash scripts

[pintomi1989]

• customer-sarahwu: Row 16 in this spreadsheet here
• customer-cisneros: Can we have /bin/bash accepted as a shell interpreter in addition to /bin/sh and /bin/zsh? We're finding scripts written in /bin/bash (which every machine in our fleet will have installed as it's a default with Ubuntu) might need to be re-written due to differences between bash and sh.
• prospect-pingouin: https://fleetdm.slack.com/archives/C07GLME5P7C/p1727895450146609
• @username: User requested this because if I can put a file on a thumb-drive, plug it into a workstation, and run it, I should be able to do that remotely.
  • @username: In the interim TODO
  • @username: Eventually TODO
• @noahtalerman: User requested this because they tried to upload a script with #!/bin/bash shebang and were confused when they saw an error message that said Fleet only supports #!/bin/sh.
  • @noahtalerman: In the interim the IT admin can remove the shebang from the first line in the script. Fleet allows the user to upload this.
  • @noahtalerman: Something to look out for is that Fleet will let a script w/o an interpreter through and always run the script with /bin/sh.
    • @allenhouchins: This means there are some scripting features unique to bash that won't work.

  • @noahtalerman: Eventually TODO

[noahtalerman]

@georgekarrv what happens if we don't specify an interpreter in the script? Do we run the script in the host's default shell? Does Fleet always run in bin/sh?

@dherder confirmed that we can upload scripts w/o an interpreter.

[dherder]

@noahtalerman I can confirm that the script will run w/o a declared interpreter.

[dherder]

@noahtalerman the script will run under /bin/sh if there is no shebang. So, with that in mind, why do we not allow for running a bash env?

[noahtalerman]

Moved original issue description here for safekeeping:

Original issue: https://github.com/fleetdm/fleet/issues/21299

Problem

/bin/bash is not currently accepted as a shell interpreter

/bin/sh and /bin/zsh are accepted

Ubuntu machines have bash installed as the default

If a customer has scripts written in bash, they need to rewrite their scripts in either sh or zsh, which is time consuming when there are a large number of scripts in question

Also, there are "bash-isms" that are not POSIX (sh) compatible:

What have you tried?

Rewriting scripts in sh or zsh

Potential solutions

Allow /bin/bash as a shell interpreter

What is the expected workflow as a result of your proposal?

Upload scripts to Fleet written in bash, and have them function properly