[Libguestfs] [libguestfs PATCH] appliance, daemon: disable lvm2 devicesfile

In guestfs-tools commit 4fe8a03cd2d3 ('sysprep: remove lvm2's default "system.devices" file', 2022-04-11), we disabled the use of LVM2's new "devicesfile" feature, which could interfere with the cloning of virtual machines. We suspected in https://bugzilla.redhat.com/show_bug.cgi?id=2072493#c6 that the same lvm2 feature could affect the libguestfs appliance itself, but decided in https://bugzilla.redhat.com/show_bug.cgi?id=2072493#c8 https://bugzilla.redhat.com/show_bug.cgi?id=2072493#c10 that this would not be the case, because "appliance/init" already constructed a pristine LVM_SYSTEM_DIR. Unfortunately, that's not enough: due to the "use_devicesfile=1" default (on RHEL9 anyway), some "lvm" invocation, possibly inside the lvm-set-filter API, *creates* "$LVM_SYSTEM_DIR/devices/system.devices". And then we get (minimally) warnings such as when using the lvm-set-filter API. Explicitly disable the "devices file" in "appliance/init", and also whenever we rewrite "lvm.conf" -- that is, in set_filter() [daemon/lvm-filter.c]. In the former, check for the feature by locating the devicesfile-related utilities "lvmdevices" and "vgimportdevices". In the C code, invoke the utilities with the "--help" option instead. (In "appliance/init", I thought it was best not to call any lvm2 utilities even with "--help", with our lvm2.conf still under construction there.) If either utility is available, set "use_devicesfile = 0". Cc: David Teigland <teigland(a)redhat.com&gt; Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1965941 Signed-off-by: Laszlo Ersek <lersek(a)redhat.com&gt; --- Notes: Tested: - on top of "master" (7afbf5ee4415), using a Fedora 35 host, where the lvm2 packages copied into the appliance do not have the "devicesfile" feature (-> regression test); - on top of "rhel-9.1" (ad24b9f4d695), in the form of a Brew scratch build, using a nightly RHEL-9.1 install, where the lvm2 packages copied into the appliance have the "devicesfile" feature (-> bugfix test). daemon/lvm-filter.c | 19 +++++++++++++++++++ appliance/init | 11 +++++++++++ 2 files changed, 30 insertions(+) diff --git a/daemon/lvm-filter.c b/daemon/lvm-filter.c index c6dd35156d37..f75e2198831e 100644 --- a/daemon/lvm-filter.c +++ b/daemon/lvm-filter.c @@ -68,6 +68,18 @@ free_lvm_system_dir (void) free (lvm_system_dir); } +static bool devicesfile_feature (void) +{ + static bool checked, available; + + if (!checked) { + checked = true; + available = command (NULL, NULL, "lvmdevices", "--help", NULL) == 0 || + command (NULL, NULL, "vgimportdevices", "--help", NULL) == 0; + } + return available; +} + /* Rewrite the 'filter = [ ... ]' line in lvm.conf. */ static int set_filter (char *const *filters) @@ -88,6 +100,13 @@ set_filter (char *const *filters) } fprintf (fp, "devices {\n"); + + /* If lvm2 supports a "devices file", we need to disable its use + * (RHBZ#1965941). + */ + if (devicesfile_feature ()) + fprintf (fp, " use_devicesfile = 0\n"); + for (j = 0; filter_types[j] != NULL; ++j) { fprintf (fp, " %s = [\n", filter_types[j]); fprintf (fp, " "); diff --git a/appliance/init b/appliance/init index 7076821d2250..19aa151b73aa 100755 --- a/appliance/init +++ b/appliance/init @@ -134,6 +134,17 @@ mdadm -As --auto=yes --no-degraded # Empty LVM configuration file means "all defaults". mkdir -p /tmp/lvm touch /tmp/lvm/lvm.conf + +# If lvm2 supports a "devices file", we need to disable its use +# (RHBZ#1965941). +if command -v lvmdevices || command -v vgimportdevices; then + { + printf 'devices {\n' + printf '\tuse_devicesfile = 0\n' + printf '}\n' + } >> /tmp/lvm/lvm.conf +fi + LVM_SYSTEM_DIR=/tmp/lvm export LVM_SYSTEM_DIR lvmetad base-commit: 7afbf5ee4415f6fa2553898d3af238e794062096 -- 2.19.1.3.g30247aa5d201