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

[Christian Ebner <c.ebner@proxmox.com>]

On 11/19/25 2:55 PM, Fabian Grünbichler wrote:
> 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@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

Ah, neat: today I learned.. Thanks!

> 
>> +
>>   	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@.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 ;)

Ack, will add that for v2

> 
>> +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..

Right, forgot to actually check the service is running after the reboot, 
only checked the output of mount for it to be mounted. Will add the 
uid=34,gid=34

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