soft-reboot: fails to boot on some environments.

[jmarrero]

@p5 experienced this: bootc-dev/bootc#1350 (comment)
and I confirmed it on a Silverblue:42 system. All my testing has been on CoreOS systems with no UI on VMs.

Need to dig deeper on what exactly is causing this.

[jmarrero]

I wonder if how/where /var is mounted is culprit here. I see what var.mount fails when booting.

On CoreOS VM I test I see:

Fedora CoreOS 42.20250815.dev.1
[core@cosa-devsh ~]$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/vda4             9.5G  2.0G  7.5G  21% /sysroot
composefs             4.8M  4.8M     0 100% /
devtmpfs              4.0M     0  4.0M   0% /dev
tmpfs                 473M     0  473M   0% /dev/shm
tmpfs                 190M  712K  189M   1% /run
tmpfs                 473M     0  473M   0% /tmp
tmpfs                 1.0M     0  1.0M   0% /run/credentials/systemd-journald.service
/dev/vda3             350M  126M  202M  39% /boot
tmpfs                 1.0M     0  1.0M   0% /run/credentials/systemd-resolved.service
/var/mnt/workdir      953G  762G  186G  81% /var/mnt/workdir
/var/mnt/workdir-tmp  953G  762G  186G  81% /var/mnt/workdir-tmp
tmpfs                 1.0M     0  1.0M   0% /run/credentials/serial-getty@ttyS0.service
tmpfs                 1.0M     0  1.0M   0% /run/credentials/getty@tty1.service
tmpfs                  95M  4.0K   95M   1% /run/user/1000

But on my machine it's same /dev device:

jmarrero@fedora ~> df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/dm-0       953G  762G  186G  81% /sysroot
composefs        23M   23M     0 100% /
devtmpfs         32G     0   32G   0% /dev
tmpfs            32G  2.2M   32G   1% /dev/shm
efivarfs        196K   57K  135K  30% /sys/firmware/efi/efivars
tmpfs            13G  2.3M   13G   1% /run
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-journald.service
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-cryptsetup@luks.service
tmpfs            32G   13M   32G   1% /tmp
/dev/dm-0       953G  762G  186G  81% /var
/dev/nvme0n1p2  974M  181M  726M  20% /boot
/dev/dm-0       953G  762G  186G  81% /var/home
/dev/nvme0n1p1  599M   13M  587M   3% /boot/efi
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-resolved.service
tmpfs           1.0M     0  1.0M   0% /run/credentials/getty@tty2.service
tmpfs           6.3G  5.7M  6.3G   1% /run/user/1000

Or maybe luks...