Bug 1569485

Created attachment 1424017 [details]
Patch to remove "method=..." if the guest is identified as Debian

Hi, reporting upstream a bug I filed in the Debian BTS, for tracking purposes. Mostly copy/paste.

Description of problem:

I'm trying to fully automatically install virtual machines by means of a
preseed file. I set "--location" to the desired URL and add some
parameters to "--extra-args" to ask debian-installer to run an automated
installation, tell it where to fetch the preseed file, and add some
parameters that I want copied to the installed system's boot
configuration (for example "elevator=noop").

This works almost perfectly, but there one slight problem: for a reason
I don't understand, virt-install adds "method=<contents of --location
option>" to the kernel parameters (qemu's "-append" option), *after* the
contents of "--extra-args".

As stated in its documentation, debian-installer will copy most kernel
parameters found after "--" or "---" to the installed system's boot
configuration (eg. in /etc/default/grub), filtering the ones it thinks
are destined to itself; so if the "--extra-args" option contains "--" or
"---", the "method=..." argument ends up being copied in
/etc/default/grub, which of course is not desired. Obviously,
debian-installer filter doesn't catch it.

Now, I'm not sure what would be the correct fix for this. I see two
possibilities:

- the conservative (and simple) one: modify virt-install to add
"method=..." *before* the contents of "--extra-args", so that if the
latter contains "--" or "---", "method=..." will be positioned before
those, and won't be copied to the installed system's boot configuration.

- the risky one: modify virt-install to not add "method=..." at all;
after re-reading debian-installer's documentation, I didn't see this
parameter mentioned anywhere. Come to think of it, this shouldn't be
needed: virt-install already fetches the kernel and initrd, and passes
them to the VM, so I can't see why debian-installer should need to know
how they were fetched.

Version-Release number of selected component (if applicable):
1.4.3

How reproducible:
Always

Steps to Reproduce:
1. Install a Debian guest with virt-install, using --location and --extra-args containing "--" or "---" (example: --extra-args "auto=true url=tftp://autoserver priority=critical --- quiet elevator=noop console=ttyS0,115200n8")
2. Log on new guest
3. Read contents of /etc/default/grub

Actual results:
/etc/default/grub contains a useless kernel parameter "method=...", because virt-install appended it to the contents of --extra-args.

Expected results:
virt-install shouldn't add this parameter, which is completely unneeded, or at least, it should prepend it to --extra-args, not append it, so that if the value of --extra-args contains "--" or "---", debian-installer won't copy it to the bootloader's configuration.

Additional info:
I attached a simple patch, which implements the second solution (remove "method=" altogether if the distribution is detected as "Debian"). It should be tested with other guest distributions though. I believe it should also check if self.name is equal to "Ubuntu", but I'm not sure of what modifications Ubuntu made to debian-installer, and thus, if ubuntu-installer needs (or support) "method=" or not.

Regards,

-- 
Raphaël Halimi