DNM: experiment with unit requirements for multipath over iscsi work

[dustymabe]

We are experimenting with iscsi and also multipath+iscsi.

In the multipath+iscsi case we end up with dependency issues in our initramfs because of coreos-multipath-wait.target:

• It blocks cryptsetup-pre.target and thus basic.target:

basic.target -> sysinit.target -> cryptsetup.target -> cryptsetup-pre.target -> coreos-multipath-wait.target -> /boot disk

• It blocks dracut-initqueue.service and that is what sets up the iscsi disks:

dracut-initqueue.service -> coreos-multipath-wait.target

I was testing this with a disk that was installed using:

sudo coreos-installer install /path/to/disk \
    --append-karg rd.multipath=default      \
    --append-karg root=/dev/disk/by-label/dm-mpath-root \
    --append-karg rw --append-karg rd.iscsi.firmware=1  \
    --console ttyS0,115200n8 -i config.ign --insecure   \
    --image-file fedora-coreos-40.20240424.dev.1-metal.x86_64.raw.xz

an a PXE config that looked like:

[dustymabe@media images]$ cat boot.ipxe 
#!ipxe
# set some random uuid as the initiator iqn, otherwise
# this will fail pointing to https://ipxe.org/1c0d6502
set initiator-iqn iqn.68cc69b9-1b54-4ff1-9d61-eedb570da8fd
sanboot iscsi:192.168.122.137::::iqn.2024-04.com.coreos:0 \
        iscsi:192.168.122.137::::iqn.2024-04.com.coreos:1

[dustymabe]

After talking with @jlebon I was able to investigate a bit more:

basic.target -> sysinit.target -> cryptsetup.target -> cryptsetup-pre.target -> coreos-multipath-wait.target -> /boot disk

This chain isn't important or rather it's not what is blocking things. It's that coreos-enable-network was blocking on basic.target, which was holding up networking and dracut-initqueue.

dracut-initqueue.service -> coreos-multipath-wait.target

This one was important. We were able to remove it.

After dropping the After=basic.target from coreos-enable-network.service and Before=dracut-initqueue.service from coreos-multipath-wait.target things seem to work.

[dustymabe]

took the output of this investigation and opened #2987