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daemon: inspect: Resolve Ubuntu 22+ /dev/disk/by-id/dm-uuid-LVM-... in fstab

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Linux + LVM supports device names like /dev/disk/by-id/dm-uuid-LVM-
followed by two concatenated UUIDs, firstly for the volume group and
secondly for the logical volume.  We can reverse those to get the
device name (/dev/VG/LV).

fstab entries look like:

  # / was on /dev/vg0/lv-0 during curtin installation
  /dev/disk/by-id/dm-uuid-LVM-OzFWT6NHkstr1hcmrWRRMDGPn9xdZj1YOOycQ533186x288FdU6UubU3OlnWJz6D / ext4 defaults 0 1
  # /usr was on /dev/vg0/lv-1 during curtin installation
  /dev/disk/by-id/dm-uuid-LVM-OzFWT6NHkstr1hcmrWRRMDGPn9xdZj1YZu53m4ZssZ8Jeb3I14RAJwIj5YlHIb9P /usr ext4 defaults 0 1

The upshot of this fix is that we are now able to correctly inspect
and run virt-v2v on Ubuntu 22+ guests with split /usr.  In particular,
we correctly map /etc/fstab entries like the above to LV device names,
which means that /usr merging now works correctly.

Reported-by: Jaroslav Spanko
Thanks: Daniel Berrange
Fixes: https://issues.redhat.com/browse/RHEL-87493
This commit is contained in:
Richard W.M. Jones
2025-04-16 10:27:25 +01:00
committed by rwmjones
parent a73f248369
commit e43ca19129
1 changed files with 21 additions and 0 deletions
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21
daemon/inspect_fs_unix_fstab.ml
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@@ -27,6 +27,7 @@ open Inspect_utils
let re_cciss = PCRE.compile "^/dev/(cciss/c\\d+d\\d+)(?:p(\\d+))?$"
let re_diskbyid = PCRE.compile "^/dev/disk/by-id/.*-part(\\d+)$"
let re_dmuuid = PCRE.compile "^/dev/disk/by-id/dm-uuid-LVM-([0-9a-zA-Z]{32})([0-9a-zA-Z]{32})$"
let re_freebsd_gpt = PCRE.compile "^/dev/(ada{0,1}|vtbd)(\\d+)p(\\d+)$"
let re_freebsd_mbr = PCRE.compile "^/dev/(ada{0,1}|vtbd)(\\d+)s(\\d+)([a-z])$"
let re_hurd_dev = PCRE.compile "^/dev/(h)d(\\d+)s(\\d+)$"
@@ -407,6 +408,26 @@ and resolve_fstab_device spec md_map os_type =
Failure _ -> default
)
(* Ubuntu 22+ uses /dev/disk/by-id/dm-uuid-LVM-... followed by a
* double UUID which identifies an LV. The first part of the UUID
* is the VG UUID. The second part is the LV UUID.
*)
else if PCRE.matches re_dmuuid spec then (
debug_matching "dmuuid";
let vg_uuid_spec = PCRE.sub 1 and lv_uuid_spec = PCRE.sub 2 in
try
(* Get the list of all VGs and LVs. *)
let vgs = Lvm_full.vgs_full () and lvs = Lvm_full.lvs_full () in
(* Find one VG & LV (hopefully) that matches the UUIDs. *)
let vg =
List.find (fun { Structs.vg_uuid } -> vg_uuid = vg_uuid_spec) vgs
and lv =
List.find (fun { Structs.lv_uuid } -> lv_uuid = lv_uuid_spec) lvs in
Mountable.of_device (sprintf "/dev/%s/%s" vg.vg_name lv.lv_name)
with
Failure _ | Not_found -> default
)
else if PCRE.matches re_freebsd_gpt spec then (
debug_matching "FreeBSD GPT";
(* group 1 (type) is not used *)