From: Filip Schauer <f.schauer@proxmox.com>
To: pve-devel@lists.proxmox.com
Subject: [pve-devel] [PATCH container] lxc config: mount /dev/shm tmpfs for application containers
Date: Tue, 2 Dec 2025 16:27:28 +0100 [thread overview]
Message-ID: <20251202152733.204787-1-f.schauer@proxmox.com> (raw)
Mount a tmpfs at /dev/shm into containers without an init system which
would normally set up a shared memory filesystem. This satisfies the OCI
Runtime Spec [0], which specifies that the following should be made
available in the container:
/proc proc
/sys sysfs
/dev/pts devpts
/dev/shm tmpfs
The reason the mount is added conditionally is to avoid interfering with
init systems: systemd correctly detects an existing /dev/shm, but OpenRC
mounts it even if already present, resulting in duplicate mounts.
[0] https://github.com/opencontainers/runtime-spec/blob/fd25dd34a06b/config-linux.md#default-filesystems
Signed-off-by: Filip Schauer <f.schauer@proxmox.com>
---
src/PVE/LXC.pm | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
index de54a0d..e5ff3a1 100644
--- a/src/PVE/LXC.pm
+++ b/src/PVE/LXC.pm
@@ -756,6 +756,11 @@ sub update_lxc_config {
$raw .= "lxc.mount.auto = sys:mixed\n";
}
+ if (defined($conf->{entrypoint}) && $conf->{entrypoint} ne '/sbin/init') {
+ # Mount /dev/shm tmpfs into the container, if no init system runs to set it up.
+ $raw .= "lxc.mount.entry = shm dev/shm tmpfs rw,nosuid,nodev,create=dir 0 0\n";
+ }
+
PVE::LXC::Config->foreach_passthrough_device(
$conf,
sub {
--
2.47.3
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