Comment 0 for bug 2003264

:$ sudo apt-get install oidentd
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
oidentd is already the newest version (2.5.0-1).
Use 'sudo apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] y
Setting up oidentd (2.5.0-1) ...
Job for oidentd.service failed because the control process exited with error code.
See "systemctl status oidentd.service" and "journalctl -xeu oidentd.service" for details.
invoke-rc.d: initscript oidentd, action "start" failed.
● oidentd.service - RFC 1413 compliant ident daemon
     Loaded: loaded (/lib/systemd/system/oidentd.service; disabled; vendor preset: enabled)
     Active: activating (auto-restart) (Result: exit-code) since Wed 2023-01-18 19:07:56 UTC; 8ms ago
    Process: 681 ExecStart=/bin/sh -c exec /usr/sbin/oidentd -S ${OIDENT_OPTIONS} -u "${OIDENT_USER}" -g "${OIDENT_GROUP}" `[ "${OIDENT_BEHIND_PROXY}" = "yes" ] && ip route show to exact 0/0 | awk '{print "-P " $3}'` (code=exited, status=1/FAILURE)

Jan 18 19:03:27 systemd[1]: oidentd.service: Failed with result 'exit-code'.
Jan 18 19:03:27 systemd[1]: Failed to start RFC 1413 compliant ident daemon.
Jan 18 19:03:30 systemd[1]: oidentd.service: Start request repeated too quickly.
Jan 18 19:03:30 systemd[1]: oidentd.service: Failed with result 'exit-code'.
Jan 18 19:03:30 systemd[1]: Failed to start RFC 1413 compliant ident daemon.
Jan 18 19:07:56 systemd[1]: oidentd.service: Control process exited, code=exited, status=1/FAILURE
Jan 18 19:07:56 1941.supergrafx.ca systemd[1]: oidentd.service: Failed with result 'exit-code'.
Jan 18 19:07:56 1941.supergrafx.ca systemd[1]: Failed to start RFC 1413 compliant ident daemon.
dpkg: error processing package oidentd (--configure):
 installed oidentd package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 oidentd
E: Sub-process /usr/bin/dpkg returned an error code (1)

/lib/systemd/system/oidentd@.service attempts to get the ip address for a proxy and fails as "ip route show" will not return an ip address under an OpenVZ install using venet devices.

:$ ip route show
default dev venet0 scope link

Additional logic needs to be included in ExecStart

You can get around this by supplying an actual ip but this is only a quick fix to get the service running.