Protip: Xen DomU crashing? Add on_crash = “preserve”

From the “many Bothans died” files

Today I had a rather lengthy issue, the full story of which can be told another time. But part of the problem was I had a DomU crashing on xl create with not much in the way of helpful error messages, like

unable to get domain type

unable to exec console client: No such file or directory

and similar.

Thanks to andyhhp in #xen on OFTC (another IRC network to add to the connect list), I added on_crash="preserve" to the DomU’s config file, which let me see the issue:

[    0.151748] Initramfs unpacking failed: junk in compressed archive
[    0.166545] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)