Simple shell script for making managing final kernel boot parameters a bit easier...

[Matthew-Tate-Scarbrough]

So anyway, after asking the other day on how to actually manage the kernel boot parameters, I knew I would be doing it a lot, so I figured I would write a script for me to be able to do that much easier. Even if it is a one-liner, if you have to do it twice, you may thrice, so it is best to write a script and document it.

I only have a year on *NIX, in general's, experience. I tried to keep the script as POSIX as I know how. It's probably not the best. Here is the link to it on my repo in which I keep my scripts: zbm_kernel_params.

In short, it reads /proc/cmdline to get the current kernel parameters. If you simply run the shell script as a oneliner, it appends the new kernel parameters:

1. zbm_kernel_params new_param1
   — or —
2. zbm_kernel_params "new_param1 new_param2"

Alternatively, it has an interactive mode, ie.

zbm_kernel_params
Enter parameters> new_param1 new_param2

And it can create a temporary file, /tmp/old_kern_params_tmp, and which it then forces the end user to edit with vi. Upon exit, these are applied and the temporary file is deleted.

zbm_kernel_params -e

And lastly, it can display the current boot parameters that should take effect (or remain in effect) at next reboot:

zbm_kernel_params -v

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I doubt it would be something you would be interested in cloning (and perhaps making a bit more straight-forward) for the project, but I am at least throwing it out there. I have tested it how I could think to, I used shellcheck. It should work as-is. The only manual intervention required would be for the end user to define their ZFS root dataset. The guide for Void on the wiki uses zroot/ROOT. I used zroot/ROOT. I think FreeBSD uses zroot/ROOT (last time I played with FBSD 12.)

[zdykstra]

Thank you for taking the time to both write this helper and to write up the detailed discussion on it! I like the ability to append parameters to the command line, as well as being able to edit it easily in vi/$EDITOR.

If you're open to a few suggestions on small changes to the script:

• Instead of using static temporary files, use mktempto create a unique temporary file on each invocation.
• Add an exit TRAP that tests for the temporary files and deletes them, so a ctrl-c doesn't leave them around
• Instead of using vi, test for $EDITOR and use that, otherwise default to vi.
• It might be nice to add a line return on whitespace when showing the org.zfsbootmenu:commandline value, to make it readable in bite-sized chunks, instead of one long line.

With some small changes (BASH-isms are fine, ZFSBootMenu has a hard dependency on Bash), this would fit nicely in the contrib/ tools section.