Fresh Virtualmin 8 / Debian Trixie install logs out Virtualmin session after “Login to Usermin”

SYSTEM INFORMATION
OS type and version Debian Linux 13
Webmin version 2.630
Usermin version 2.530
Virtualmin version 8.1.0 Professional
Theme version 26.30
Apache version 2.4.67
Package updates 61 package updates are available

I’ve got multiple older servers originally installed on Debian Bookworm with Virtualmin 7 and later upgraded to Virtualmin 8. On all of those, using “Login to Usermin” from Virtualmin works correctly and the original Webmin/Virtualmin session remains active.

However, on a fresh Debian Trixie + Virtualmin 8 install, clicking “Login to Usermin” successfully logs into Usermin, but when returning to Virtualmin/Webmin the original session has expired and I need to log in again.

After comparing configs between a working older server and the new Trixie install, I found this difference:

Working server:

  • /etc/webmin/miniserv.conf → no sidname
  • /etc/usermin/miniserv.confsidname=usid

Fresh Trixie / VM8 install:

  • /etc/webmin/miniserv.confsidname=usid
  • /etc/usermin/miniserv.confsidname=usid

So on the new install both Webmin and Usermin appear to be using the same session cookie name.

This seems likely to be the cause of the issue, as logging into Usermin may overwrite the existing Webmin session cookie.

Before changing anything manually, I wanted to check:

  • Is this expected behaviour on newer installs?
  • Was there a deliberate change causing Webmin to also use sidname=usid?
  • Is this a known issue with fresh VM8/Trixie installs?

Thanks,
Seb