Fix Proxmox Web Interface Login Errors; a Step-by-Step Guide

By Lucas Fernandes Aguiar

This article details a troubleshooting process for a Proxmox cluster authentication failure that prevented users from logging into the web interface. The root cause was identified as a missing /etc/pve/access.cfg file, crucial for user authentication, likely due to corosync communication issues. The problem was resolved by restarting the pve-cluster service, forcing quorum, manually creating a minimal access.cfg file, and restarting the pveproxy service. Preventative measures include regular cluster health checks, automated configuration file backups, ensuring proper shutdown procedures, maintaining network stability, monitoring storage health, applying Proxmox updates, and careful permissions management.

Initial Investigation

  1. Service Status: Checked the status of pve-cluster and pveproxy services, which were running.
  2. Logs: Examined logs for errors related to RRD database updates.
  3. Authentication Configuration: Verified /etc/pve/user.cfg.
  4. Missing Configuration File: Discovered that /etc/pve/access.cfg was missing.
  5. Firewall Interference: Suspected Tailscale firewall rules might be interfering. Attempted to adjust iptables.

Here are the commands used during the investigation:

# 1. Check service status
systemctl status pve-cluster
systemctl status pveproxy

# 2. Check logs for errors
journalctl -u pveproxy -n 100
journalctl -u pve-cluster -n 100
tail -n 100 /var/log/pveproxy/access.log

# 3. Verify authentication configuration
cat /etc/pve/user.cfg
ls -la /etc/pve/user.cfg

# 4. Check for missing access.cfg
ls -la /etc/pve/access.cfg
file /etc/pve/access.cfg

# 5. Check firewall rules and Tailscale status
iptables -L -n -v
tailscale status
systemctl status tailscaled

Root Cause Analysis

The primary cause of the login issue was the absence of the /etc/pve/access.cfg file. This file is crucial for user authentication in Proxmox. Its absence indicated a potential problem with the Proxmox cluster configuration, possibly related to the corosync service.

Further investigation revealed issues with corosync connectivity and permissions related to pve-ha-lrm. Although corosync was running, errors indicated communication problems within the cluster. The /etc/pve/access.cfg file wasn’t being automatically generated or populated, leading to authentication failures.

The filesystem check on /etc/pve showed it was a FUSE filesystem, making underlying storage issues less likely, focusing the investigation on the cluster configuration itself.

Solution

The following steps were taken to resolve the issue:

  1. Restarted pve-cluster service: Stopped and started the pve-cluster service to attempt to re-establish cluster connectivity.
  2. Forced Quorum: This step potentially helped to re-establish cluster leadership.
  3. Created access.cfg file: Manually created the /etc/pve/access.cfg file with minimal content.
  4. Restarted pveproxy service: Restarted the pveproxy service to force it to recognize the newly created access.cfg file.

Here are the commands used to implement the solution:

# 1. Restart pve-cluster service
systemctl stop pve-cluster
systemctl start pve-cluster
systemctl status pve-cluster

# 2. Force quorum in a single-node setup
pvecm expected 1

# 3. Create minimal access.cfg file
cat > /etc/pve/access.cfg << 'EOF'
acl:1
path /
role Administrator
user root@pam
EOF

chmod 0640 /etc/pve/access.cfg
chown root:www-data /etc/pve/access.cfg

# 4. Restart pveproxy service
systemctl restart pveproxy
systemctl status pveproxy

After these steps, users were able to log in to the Proxmox web interface successfully.

Additional Notes

  • If the login still fails after these steps, further investigation into user permissions and the contents of access.cfg may be required. The pveum command-line tools can be used to manage users and permissions.

Prevention measures

Preventing the “Proxmox Authentication Failure due to Missing Cluster Configuration File” error involves ensuring the stability and proper functioning of the Proxmox cluster and its configuration files. Here are several strategies:

  1. Regular Cluster Health Checks:

  • Implement automated monitoring of the Proxmox cluster’s health. This should include checks for:

  • Corosync quorum status: Ensure the cluster maintains a quorum to prevent configuration inconsistencies.

  • Service status: Monitor the status of critical services like pve-cluster, pveproxy, corosync, pve-ha-lrm, and pve-ha-crm.

  • Log analysis: Regularly scan logs for errors or warnings related to cluster communication, authentication, and storage.

  1. Configuration File Backups:
  • Automate regular backups of the /etc/pve directory. This allows for quick restoration of configuration files in case of accidental deletion or corruption.
  1. Proper Shutdown Procedures:
  • Ensure that all Proxmox nodes are shut down gracefully. Avoid abrupt shutdowns or power outages, as these can lead to data corruption or configuration inconsistencies.
  1. Network Stability:
  • Maintain a stable and reliable network connection between the Proxmox nodes. Network disruptions can lead to cluster instability and configuration issues.
  1. Storage Health Monitoring:
  • Monitor the health of the underlying storage used by the Proxmox cluster. Storage failures can lead to data loss and configuration corruption.
  1. Proxmox Updates and Patches:
  • Keep the Proxmox installation up to date with the latest updates and security patches. These updates often include bug fixes and improvements that can enhance cluster stability.
  1. Permissions Management:
  • Review and manage file permissions within the /etc/pve directory. Ensure that the correct users and groups have the necessary permissions to access and modify configuration files.
  • Avoid making manual changes to files in /etc/pve unless absolutely necessary, and always back up the original file before making any changes.
  1. Cluster Awareness during Maintenance:
  • When performing maintenance on any node in the cluster, ensure that the other nodes are aware of the maintenance and can maintain quorum. Consider using Proxmox’s built-in maintenance mode.
  1. Implement redundancy
  • Consider having multiple nodes. If /etc/pve/access.cfg is missing on one node, it can be copied over from another.

By implementing these preventative measures, you can significantly reduce the risk of encountering the “Proxmox Authentication Failure due to Missing Cluster Configuration File” error and ensure the stability and reliability of your Proxmox cluster.

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