SysTutorials

Fix “sulogin: can not open password database” on Linux

· Eric Ma

When Linux fails to boot with the error message “sulogin: can not open password database” despite /etc/passwd and /etc/shadow appearing intact, SELinux is often the culprit. The files exist and have correct content, but SELinux context labels are missing or corrupted, preventing the login process from reading them.

Diagnose the Problem

Boot into the initramfs emergency shell to confirm the issue. The error typically occurs during the early boot phase when systemd tries to spawn the sulogin session. You’ll see the error repeatedly without getting a login prompt.

Solution: Boot into Read-Write Mode and Fix SELinux

Step 1: Reboot with read-write root and shell access

Reboot your system and interrupt the GRUB menu (press e on the boot entry). Find the linux line and append:

rw init=/bin/bash

This boots directly to a bash shell with a read-write root filesystem, bypassing normal SELinux policy enforcement.

Step 2: Disable SELinux temporarily

Once at the shell prompt, run:

setenforce 0

This sets SELinux to permissive mode, allowing the system to boot normally.

Step 3: Reboot normally

reboot

If the system boots successfully, the issue is confirmed as SELinux context corruption.

Permanent Fix: Restore SELinux Contexts

Once logged in normally, restore the correct SELinux contexts on authentication files:

sudo restorecon -v /etc/passwd /etc/shadow /etc/group /etc/gshadow

For a more thorough fix across the entire system:

sudo restorecon -Rv /etc

If you need to relabel the entire filesystem:

sudo touch /.autorelabel
sudo reboot

This creates a flag that triggers a full SELinux relabel on the next boot. On modern systems, this can take 10-30 minutes depending on disk size.

Verify SELinux is Enforcing Again

After the system boots and relabels (if you used .autorelabel), confirm SELinux is back in enforcing mode:

getenforce

Should return Enforcing. If you manually set it to permissive, re-enable it:

sudo setenforce 1

Check for Filesystem Issues

If relabeling doesn’t resolve the problem, verify the filesystem itself:

sudo fsck -n /

(The -n flag does a read-only check without modifications. Remove -n to actually repair if needed, but only on unmounted filesystems.)

Prevention

SELinux context corruption often occurs from:

Keep your system updated and always use proper shutdown procedures:

sudo dnf update -y
sudo systemctl reboot

Avoid force-killing the system or hard power cycles when possible.

Troubleshooting Common Issues

When encountering problems on Linux systems, follow a systematic approach. Check system logs first using journalctl for systemd-based distributions. Verify service status with systemctl before attempting restarts. For network issues, use ip addr and ss -tulpn to diagnose connectivity problems.

Package management issues often stem from stale caches. Run dnf clean all on Fedora or apt clean on Ubuntu before retrying failed installations. If a package has unmet dependencies, try resolving them with dnf autoremove or apt autoremove.

These commands are frequently used alongside the tools discussed in this article:

Quick Verification

After applying the changes described above, verify that everything works as expected. Run the relevant commands to confirm the new configuration is active. Check system logs for any errors or warnings that might indicate problems. If something does not work as expected, review the steps carefully and consult the official documentation for your specific version.

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