[pbs-devel] [PATCH proxmox-backup] etc: provide and enable mount unit for /run/proxmox-backup

[Fabian Grünbichler]

On November 19, 2025 2:15 pm, Christian Ebner wrote:
> Since the introduction of per-chunk file locks for datastores with s3
> backend, the inodes on the tmpfs backing /run/proxmox-backup might be
> to limited, the kernel dynamically calculating the limit based on
> available system memory [0]. To not limit the number of inodes,
> provide a systemd mount unit to create a dedicated tmpfs for
> /run/proxmox-backup and only enable this for now so it becomes
> effective on reboot, since this cannot be safely started now.
> 
> [0] https://docs.kernel.org/filesystems/tmpfs.html
> 
> Fixes: https://forum.proxmox.com/threads/176228/
> Signed-off-by: Christian Ebner <c.ebner at proxmox.com>
> ---
>  debian/postinst                      |  2 ++
>  debian/proxmox-backup-server.install |  1 +
>  "etc/run-proxmox\\x2dbackup.mount"   | 13 +++++++++++++
>  3 files changed, 16 insertions(+)
>  create mode 100644 "etc/run-proxmox\\x2dbackup.mount"
> 
> diff --git a/debian/postinst b/debian/postinst
> index 8b5e9bbed..0fddfbd99 100644
> --- a/debian/postinst
> +++ b/debian/postinst
> @@ -25,6 +25,8 @@ case "$1" in
>  	fi
>  	deb-systemd-invoke $_dh_action proxmox-backup.service proxmox-backup-proxy.service >/dev/null || true
>  
> +	systemctl enable run-proxmox\\x2dbackup.mount >/dev/null || true

this is not needed, by virtue of installing the unit this is already
handled by dh_installsystemd (which we override to only enable, but not
start/restart units), which inserts the following into the postinst (and
a corresponding snippet for puring the package into postrm):

# Automatically added by dh_installsystemd/13.24.2
if [ "$1" = "configure" ] || [ "$1" = "abort-upgrade" ] || [ "$1" = "abort-deconfigure" ] || [ "$1" = "abort-remove" ] ; then
        # The following line should be removed in trixie or trixie+1
        deb-systemd-helper unmask 'run-proxmox\x2dbackup.mount' >/dev/null || true

        # was-enabled defaults to true, so new installations run enable.
        if deb-systemd-helper --quiet was-enabled 'run-proxmox\x2dbackup.mount'; then
                # Enables the unit on first installation, creates new
                # symlinks on upgrades if the unit file has changed.
                deb-systemd-helper enable 'run-proxmox\x2dbackup.mount' >/dev/null || true
        else
                # Update the statefile to add new symlinks (if any), which need to be
                # cleaned up on purge. Also remove old symlinks.
                deb-systemd-helper update-state 'run-proxmox\x2dbackup.mount' >/dev/null || true
        fi
fi
# End automatically added section


> +
>  	if test -n "$2"; then
>  		# FIXME: Remove in future version once we're sure no broken entries remain in anyone's files
>  		if grep -q -e ':termproxy::[^@]\+: ' /var/log/proxmox-backup/tasks/active; then
> diff --git a/debian/proxmox-backup-server.install b/debian/proxmox-backup-server.install
> index d06f026cf..11dd037e8 100644
> --- a/debian/proxmox-backup-server.install
> +++ b/debian/proxmox-backup-server.install
> @@ -6,6 +6,7 @@ etc/proxmox-backup-daily-update.timer /usr/lib/systemd/system/
>  etc/proxmox-backup-proxy.service /usr/lib/systemd/system/
>  etc/proxmox-backup.service /usr/lib/systemd/system/
>  etc/removable-device-attach at .service /usr/lib/systemd/system/
> +etc/run-proxmox\x2dbackup.mount /usr/lib/systemd/system/
>  usr/bin/pmt
>  usr/bin/pmtx
>  usr/bin/proxmox-tape
> diff --git "a/etc/run-proxmox\\x2dbackup.mount" "b/etc/run-proxmox\\x2dbackup.mount"
> new file mode 100644
> index 000000000..f5fbe2eb4
> --- /dev/null
> +++ "b/etc/run-proxmox\\x2dbackup.mount"
> @@ -0,0 +1,13 @@
> +[Unit]
> +Description=Mount tmpfs at /run/proxmox-backup
> +Conflicts=umount.target
> +Before=local-fs.target umount.target
> +
> +[Mount]
> +Type=tmpfs
> +What=tmpfs
> +Where=/run/proxmox-backup

might be good to have a comment here *why* we do nr_inodes=0 ;)

> +Options=rw,nosuid,nodev,noexec,relatime,nr_inodes=0,mode=755,inode64

and the options here mean that /run/proxmox-backup is

Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)

instead of the previous 755 but owned by backup:backup, so we need to
also include uid and gid backup in the mountoptions here, else the proxy
will fail to start after a reboot..

> +
> +[Install]
> +WantedBy=local-fs.target
> -- 
> 2.47.3
> 
> 
> 
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