** Description changed: [Impact] On Ubuntu VMs running under Microsoft Hyper-V, users commonly rely on 'hv_sock' (Hyper-V socket) to enable seamless SSH access using the 'hvc.exe' tool on the Windows host. This works correctly on Ubuntu Jammy and earlier ( and Oracular and later with different mechanism ), but fails silently in Noble due to a missing '[email protected]' systemd unit. The failure is due to a combination of systemd and OpenSSH changes: * In older versions (e.g., Jammy with systemd 249), the '[email protected]' unit was relied upon for socket activation ('Accept=yes' mode) and the unit file exists. * With the Ubuntu Kinetic release, '[email protected]' was removed, and no template unit was shipped by default. * systemd introduced systemd-ssh-generator in version 256 checks [email protected] unit and openssh provides [email protected] unit. * Ubuntu Noble ships with systemd 255, which lacks this feature, resulting in the absence of [email protected]. * Debian has restored a static '[email protected]' template in recent OpenSSH packaging. Noble’s OpenSSH package currently lacks it. As a result, the typical 'ssh.socket' activation workflow fails on Noble, breaking compatibility for 'hv_sock' SSH access. This issue affects all Ubuntu series between Kinetic and Noble (inclusive) where: * systemd < 256 is used (no dynamic generator) * '[email protected]' has been removed But I think Noble only needs SRU for now since the others are EOL. Basically user should setup ssh.socket correctly to use hv_sock(e.g changing Accept=no to Accept=yes) but creating whole service file ([email protected]) might be different story since Jammy was working fine. [Test Case] 1. Launch a Noble VM on Hyper-V. 2. Ensure the 'hv_sock' kernel module is loaded: echo 'hv_sock' >> /etc/modules 3. Adding the socket conf for SSH to listen on vsock: # cat > /etc/systemd/system/ssh.socket.d/vsock.conf << EOF [Socket] - ListenStream=vsock:22 + ListenStream=vsock::22 Accept=yes EOF 4. Reload and reconfigure systemd units: systemctl disable ssh.service systemctl daemon-reload systemctl stop ssh.service systemctl enable ssh.socket systemctl start ssh.socket 5. Attempt to connect from the Hyper-V host: hvc ssh user@ubuntu-vm Expected Result: Connection succeeds and SSH login is presented. Actual Result: The connection hangs. No systemd unit is spawned due to missing '[email protected]'. [Where problems could occur] Adding a static '[email protected]' template unit, as done in Debian(although it is [email protected]), is unlikely to interfere with traditional SSH service setups (i.e., 'ssh.service'). The '@' template only activates in conjunction with 'Accept=yes' sockets and does not conflict with existing unit files. Also it was working in Jammy. [Other Info] * Debian commit restoring '[email protected]' https://salsa.debian.org/ssh-team/openssh/-/commit/eb25ab611967996a0d57b4ee565faa7de58b41f6 * systemd 256 adding 'systemd-ssh-generator' https://github.com/systemd/systemd/commit/0e3220684c6184a2f70396d991200ae207a25377 * OpenSSH in Ubuntu removed '[email protected]' in https://launchpadlibrarian.net/619116456/openssh_1%3A9.0p1-1_1%3A9.0p1-1ubuntu1.diff.gz during Kinetic development.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2111226 Title: [email protected] is still needed for hv_sock in Noble release To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/2111226/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
