Fixup location of boot cdrom repository

[jandubois]

The boot iso is sometimes mounted as /media/cdrom but more often as /media/sr0.

I haven't been able to figure out why.

[jandubois]

Note that this PR is mostly cosmetic, to get rid of this kind of warning:

WARNING: opening /media/cdrom/apks: No such file or directory

All the packages from the boot ISO have already been installed during the boot process, so are not really needed for normal use-cases. I still wanted to silence the warning though.

[AkihiroSuda]

Thanks, but I wonder why this can't be deterministic

[jandubois]

I wonder why this can't be deterministic

Me too, but I couldn't figure it out. It is probably some kind of race condition. It sometimes (maybe 1 out of 4) happens on the first boot:

lima-alpine:~# mount | grep media
/dev/sr0 on /media/cdrom type iso9660 (ro,relatime,nojoliet,check=s,map=n,blocksize=2048,iocharset=utf8)

But on reboot it then looks like

lima-alpine:~# mount | grep media
/dev/sr0 on /media/sr0 type iso9660 (ro,relatime,nojoliet,check=s,map=n,blocksize=2048,iocharset=utf8)

I don't think I've seen /media/cdrom being used after a reboot, only sometime on first boot. But I didn't keep proper notes to know for sure.

/media/cdrom is listed in /etc/fstab:

lima-alpine:~# grep cdrom /etc/fstab
/dev/cdrom	/media/cdrom	iso9660	noauto,ro 0 0

I don't know how /media/sr0 is being mounted, but if that happens first, then the mount of /media/cdrom will fail because they both mount the same device (/dev/cdrom is just a symlink to /dev/sr0):

lima-alpine:~# ls -l /dev/cdrom
lrwxrwxrwx    1 root     root             3 Jan 15 20:25 /dev/cdrom -> sr0

We could try to remove the /dev/cdrom line from /etc/fstab in the ISO image. I suspect that we would then consistently see /media/sr0 all the time, but I have no energy now to run further experiments. I can do this tomorrow, if you prefer that change to the ISO over adding this PR. Just let me know!

[AkihiroSuda]

We could try to remove the /dev/cdrom line from /etc/fstab in the ISO image. I suspect that we would then consistently see /media/sr0 all the time, but I have no energy now to run further experiments. I can do this tomorrow, if you prefer that change to the ISO over adding this PR. Just let me know!

Thanks, 👍 on consistent /media/sr0

[jandubois]

This PR will be obsolete once lima-vm/alpine-lima#121 is used in the Alpine image. It removes the /media/cdrom mount point from /etc/fstab, so /dev/sr0 will always be mounted to /media/sr0.

[jandubois]

I've confirmed with the below script that with an empty /etc/fstab I only ever see /media/sr0:

#!/usr/bin/env bash
set -xeu
count=0
while [[ "$count" -lt 100 ]]; do
    printf "\e[0;1;32mcount=%d\e[0m\n" "${count}"
    limactl delete -f alpine || true
    limactl start --tty=false template://alpine
    mp=$(limactl shell alpine cat /proc/mounts | awk '$1 == "/dev/sr0" {print $2}')
    if [[ $mp != /media/sr0 ]]; then
        echo Mountpoint is $mp
        exit 1
    fi
    count=$((count+1))
done

I was worried that the /etc/fstab would only be installed from the apkovl file after /media/cdrom has potentially already been mounted, but that doesn't seem to be the case (or it is unmounted again).

I've also run a modified version of that script that creates the VM only once, and then just stops and restarts it. It confirmed that /media/cdrom was only ever seen on first-boot.