Hello all, I haven’t been here for ages (the system says almost five years) in the meantime I have thought that I have learned plenty about Linux, but it turns out that I might have overestimated my abilities because I do not have any clue what is happening. I’ll try to start from the beginning and add as many details as I can recall. If you need some additional info please type the command on how to obtain it.
I am running Proxmox 7.3-3 on a NUC, actually, it is a cluster of two NUCs, but that part is not important. One of the VM guests is Debian 11 (with GUI) whose primary function is to be a Docker host for docker containers living in my local network (currently Jellyfin, Monica, Universal Media Server, and AudioBookshelf). I have used it for months with regular updates and thought yesterday about restarting it. I had added some of the mounts that were not permanent before to /etc/fstab and wanted to see if anything would change after the reboot. The other change I have made is that I added +4GB of RAM because I have seen that the machine was often using more than 90% of the 4GB it initially had.
Here just to make it clear, Proxmox works fine, the problem is with Debian guest, and since I do not have a snapshot of that VM, repairing it might be a nice learning experience.
After the restart, I am welcomed to a frozen GUI. My initial thought was that I have wretched something in the fstab so I restarted it in recovery mode and commented out the three rows (CIFS mounts) I have added. Restated. Found the same problem. Next, I installed SSH and tried to access it from another machine, but there were some problems also. I was greeted by the message ** Access denied for user by PAM account configuration**. That one I have solved that one by circumventing it. First I tried adding +:user:ALL to /etc/security/access.conf, but when that did not pan out I solved it by toggling UsePAM to no in /etc/ssh/sshd_config. After that, I have been granted SSH access for my non-root user. I would like to know a more elegant (secure) solution to this problem, but it is not the main problem now.
After starting the system in regular mode, and with the CIFS mounts uncommented again I could find out that all the docker services work fine, just that I still have the frozen GUI.
My problem there is that I have no clue what could have gone wrong, what log file is associated with the working of the GUI, and how to find what the problem is. My experience with Linux is that the problem is usually simple to solve if one can understand what the problem is. But, here, I have a problem understanding what the problem is and where/how to find information about it.
TLDR:
After a restart, Debian 11 GUI is frozen, all the background services work fine. I have SSH access from another machine and docker containers are running and their services are accessible.