r350184 changed login(1) to read /var/run/motd.
As been noted in
there is a need to support displaying an immutable motd with specific exact text at login.
To keep motd immutable and prevent it being prepended with uname output,
update_motd needs to be set to "NO" in rc.conf to not generate /var/run/motd.
An immutable motd file can then can be created in /var/run
but if it is a tmpfs, the file will not survive a reboot.
Phabricator review to change login(1) back to reading /etc/motd.
This allows using /etc/motd as a regular file when update_motd="NO".
update_motd="YES" causes /etc/motd to be created as a symbolic link to /var/run/motd so login(1) will still read it.
The problem also affects update_motd="NO" when not using tmpfs for /var/run.
cleanvar_enable="YES" by default and cleanvar scripts removes files under /var/run so if motd is created there manually it will be deleted after reboot.