Support for running commands in the installer

[bsiegert]

As you probably know, I am using Anita in netbsd-gce.
The way the script works now, Anita is doing the installation, then the emulator boots into the newly installed system to do a few minor things. The only one that's absolutely necessary is to set a lower MTU for the vio network interface.

I would like to start a conversation on how to avoid that first boot, since it means that a number of first-boot scripts are run on the system. Notably, this means every instance created from one instance template has the same SSH host key, which is not great.

Do you think it would make sense to add support for running commands in the installer, i.e. dropping to a shell after the install and running some commands there? It would be simple to create /etc/ifconfig.vioif0 in that environment, for instance.

Alternatively, I could see a simpler workaround, such as removing the rc_configured variable from /etc/rc.conf after making modifications to the system, so that the first-boot script is run again.

What do you think?

[gson1703]

As you probably know, I am using Anita in netbsd-gce. The way the script works now, Anita is doing the installation, then the emulator boots into the newly installed system to do a few minor things.

Have you considered basing this on an amd64 live image as built by "build.sh live-image" instead of installing using anita? It's a shame pre-built live images are still not included in the official binary releases...

The only one that's absolutely necessary is to set a lower MTU for the vio network interface.

Out of curiosity, why is that necessary? NetBSD bug or GCE bug?

I would like to start a conversation on how to avoid that first boot, since it means that a number of first-boot scripts are run on the system. Notably, this means every instance created from one instance template has the same SSH host key, which is not great.

Presumably it will also have the same entropy seed file, and that's going to be a problem even if you avoid the first boot.

Do you think it would make sense to add support for running commands in the installer, i.e. dropping to a shell after the install and running some commands there? It would be simple to create /etc/ifconfig.vioif0 in that environment, for instance.

Regardless of whether or not anita is the right tool for the GCE job, I do think this would be a reasonable feature to add, perhaps as a "--run-post-install" option working similarly to the existing "--run" but running at the end of the install stage rather than after boot.

Alternatively, I could see a simpler workaround, such as removing the rc_configured variable from /etc/rc.conf after making modifications to the system, so that the first-boot script is run again.

What do you think?

Another option that comes to mind is that instead of booting the freshly installed target image, you could boot a different image that mounts the target image and configures its MTU, etc. Or to avoid the need for a second image, maybe boot the target image in qemu passing the same image as two different virtual drives, a boot drive with snapshot=on so that the ssh keys don't get written persistently, and as a non-boot drive with snapshot=off to mount and configure.

[gson1703]

I forgot to say, if a --run-post-install option is added, it should be machine independent, which means it can't work by dropping to a shell in the sense of exiting sysinst, because that won't work on sparc, for example. But it could probably work by running a shell from the sysinst Utility Menu at the end of installation.

Please send patches or a pull request :)