[pve-devel] [PATCH container v4 20/27] backup: implement backup for external providers

[Fiona Ebner]

The filesystem structure is made available as a directory in a
consistent manner (with details depending on the vzdump backup mode)
just like for regular backup via tar.

The backup_container() method of the backup provider is executed in
a user namespace with the container's ID mapping applied. This allows
the backup provider to see the container's filesystem from the
container's perspective.

The 'prepare' phase of the backup hook is executed right before and
allows the backup provider to prepare for the (usually) unprivileged
execution context in the user namespace.

The backup provider needs to back up the guest and firewall
configuration and the filesystem structure of the container, honoring
file exclusions and the bandwidth limit.

Signed-off-by: Fiona Ebner <f.ebner at proxmox.com>
---

Changes in v4:
* run_in_userns() helper now lives in LXC::Namespaces module
* log which backup mechanism is used

 src/PVE/VZDump/LXC.pm | 40 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 39 insertions(+), 1 deletion(-)

diff --git a/src/PVE/VZDump/LXC.pm b/src/PVE/VZDump/LXC.pm
index 1928548..0a6f2c3 100644
--- a/src/PVE/VZDump/LXC.pm
+++ b/src/PVE/VZDump/LXC.pm
@@ -11,6 +11,7 @@ use PVE::Cluster qw(cfs_read_file);
 use PVE::GuestHelpers;
 use PVE::INotify;
 use PVE::LXC::Config;
+use PVE::LXC::Namespaces;
 use PVE::LXC;
 use PVE::Storage;
 use PVE::Tools;
@@ -124,6 +125,7 @@ sub prepare {
 
     my ($id_map, $root_uid, $root_gid) = PVE::LXC::parse_id_maps($conf);
     $task->{userns_cmd} = PVE::LXC::userns_command($id_map);
+    $task->{id_map} = $id_map;
     $task->{root_uid} = $root_uid;
     $task->{root_gid} = $root_gid;
 
@@ -373,7 +375,43 @@ sub archive {
     my $userns_cmd = $task->{userns_cmd};
     my $findexcl = $self->{vzdump}->{findexcl};
 
-    if ($self->{vzdump}->{opts}->{pbs}) {
+    if (my $backup_provider = $self->{vzdump}->{'backup-provider'}) {
+	$self->loginfo("starting external backup via " . $backup_provider->provider_name());
+
+	if (!scalar($task->{id_map}->@*) || $task->{root_uid} == 0 || $task->{root_gid} == 0) {
+	    $self->log("warn", "external backup of privileged container can only be restored as"
+		." unprivileged which might not work in all cases");
+	}
+
+	my ($mechanism) = $backup_provider->backup_get_mechanism($vmid, 'lxc');
+	die "mechanism '$mechanism' requested by backup provider is not supported for containers\n"
+	    if $mechanism ne 'directory';
+
+	$self->loginfo("using backup mechanism '$mechanism'");
+
+	my $guest_config = PVE::Tools::file_get_contents("$tmpdir/etc/vzdump/pct.conf");
+	my $firewall_file = "$tmpdir/etc/vzdump/pct.fw";
+
+	my $info = {
+	    directory => $snapdir,
+	    sources => [@sources],
+	    'backup-user-id' => $task->{root_uid},
+	};
+	$info->{'firewall-config'} = PVE::Tools::file_get_contents($firewall_file)
+	    if -e $firewall_file;
+	$info->{'bandwidth-limit'} = $opts->{bwlimit} * 1024 if $opts->{bwlimit};
+
+	$backup_provider->backup_hook('prepare', $vmid, 'lxc', $info);
+
+	if (scalar($task->{id_map}->@*)) {
+	    PVE::LXC::Namespaces::run_in_userns(
+		sub { $backup_provider->backup_container($vmid, $guest_config, $findexcl, $info); },
+		$task->{id_map},
+	    );
+	} else {
+	    $backup_provider->backup_container($vmid, $guest_config, $findexcl, $info);
+	}
+    } elsif ($self->{vzdump}->{opts}->{pbs}) {
 
 	my $param = [];
 	push @$param, "pct.conf:$tmpdir/etc/vzdump/pct.conf";
-- 
2.39.5