[pve-devel] [PATCH ifupdown2] debian: postinst: ensure /etc/iproute2/rt_tables.d exists

[Michael Köppl]

Since I was just not encountering this problem (again), gave this patch
a quick spin on my Trixie dev VM. Was able to `ifreload -a` without
warnings again and apply networking changes through the UI without
encountering errors in the task log. As before, any changes are applied
successfully, just without the warnings.

Tested-by: Michael Köppl <m.koeppl at proxmox.com>

On 7/8/25 18:43, Friedrich Weber wrote:
> When upgrading to Debian Trixie, iproute2 is also upgraded. Its
> postinst deletes /etc/iproute2/rt_tables.d if it is currently empty
> (or only contains a README file) [1]. After that, ifreload -a will
> always print a warning:
> 
>> error: [Errno 2] No such file or directory: '/etc/iproute2/rt_tables.d/ifupdown2_vrf_map.conf'
> 
> because it cannot create the file if the parent directory does not
> exist.
> 
> To avoid that, create the directory in ifupdown2's postinst if it
> does not exist yet.
> 
> Commit b115f7f ("add /etc/iproute2/rt_tables.d/ to managed
> directories") already added the directory to ifupdown2.dirs, but this
> does not seem to be effective, due to the following sequence of events
> on upgrade:
> 
> 1) iproute2 is unpacked
> 2) ifupdown2 is unpacked. The directory still exists, so the
>    ifupdown2.dirs entry does not have an effect
> 3) ifroute2 is set up, and its postinst empties and removes the
>    directory
> 4) ifupdown2 is set up
> 
> [1] https://sources.debian.org/src/iproute2/6.15.0-1/debian/iproute2.postinst/
> 
> Signed-off-by: Friedrich Weber <f.weber at proxmox.com>
> ---
> 
> Notes:
>     Please check the reasoning for plausibility, my understanding of dpkg
>     is very basic, this is just what I could infer from running strace on
>     the upgrade.
>     
>     An alternative solution would be to patch ifupdown2 itself to create
>     the directory (if needed) before trying to write to the
>     ifupdown2_vrf_map.conf file.
> 
>  debian/ifupdown2.postinst | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/debian/ifupdown2.postinst b/debian/ifupdown2.postinst
> index f9a719c..13cc987 100644
> --- a/debian/ifupdown2.postinst
> +++ b/debian/ifupdown2.postinst
> @@ -111,6 +111,9 @@ case "$1" in
>          process_udev
>          chmod +x /usr/share/ifupdown2/__main__.py
>          postinst_remove_diverts
> +        if [ ! -d /etc/iproute2/rt_tables.d ]; then
> +            mkdir /etc/iproute2/rt_tables.d || echo "could not create /etc/iproute2/rt_tables.d"
> +        fi
>          if [ -z "$2" ] && [ ! -e /proxmox_install_mode ]; then
>              proxmox_compatibility
>              echo "Reloading network config on first install"