If your server fails to boot, it can be caused by filesystem corruption, misconfigured boot settings, a failed update, or a full disk. This guide walks you through diagnosing and repairing boot issues using the web console and rescue mode.

Symptoms of Boot Failure

• Server shows as "Running" in the dashboard but is unreachable via SSH.
• The web console shows error messages during boot (kernel panic, filesystem errors, GRUB errors).
• The server is stuck at a boot prompt or login screen but does not respond.
• Dashboard shows the server repeatedly restarting.

Step 1 — Check the Web Console

The web console is your primary diagnostic tool when SSH is unavailable:

See Using the Web Console for console details.

Common Boot Error Messages

Step 2 — Boot Into Rescue Mode

If normal boot fails, boot into rescue mode:

Rescue mode boots a minimal Linux environment from a separate image, giving you access to your server's disk without loading its operating system.

Step 3 — Mount the Server's Filesystem

In rescue mode, mount your server's disk:

# List available disks
lsblk
Mount the main partition (adjust device name as needed)
mount /dev/vda1 /mnt
If using LVM
vgscan
vgchange -ay
mount /dev/mapper/vg0-root /mnt

Once mounted, you can access and repair files on your server's disk.

Common Fixes

Fix Filesystem Corruption

# Unmount first (if mounted)
umount /mnt
Run filesystem check
fsck -y /dev/vda1
Remount after repair
mount /dev/vda1 /mnt

Fix a Full Disk

# Check disk usage
df -h /mnt
Find large files
du -sh /mnt/var/log/*
du -sh /mnt/tmp/*
Clean up logs
truncate -s 0 /mnt/var/log/syslog
rm -f /mnt/var/log/*.gz
Clear package cache
rm -rf /mnt/var/cache/apt/archives/*.deb

Fix a Failed Service Blocking Boot

# Chroot into the mounted system
mount --bind /dev /mnt/dev
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
chroot /mnt
Disable the problematic service
systemctl disable problematic-service
Exit chroot
exit

Fix SSH Configuration

If a misconfigured SSH prevents access:

# Edit the SSH config on the mounted disk
nano /mnt/etc/ssh/sshd_config
Fix the issue (e.g., restore PermitRootLogin, fix port number)
Save and exit

Restore GRUB

# Chroot into the mounted system
chroot /mnt
Reinstall GRUB
grub-install /dev/vda
update-grub
Exit chroot
exit

Step 4 — Reboot Normally

After making repairs:

Prevention

• Keep disk usage below 85% — A full disk is a common cause of boot failure.
• Test updates — Apply major updates during maintenance windows.
• Create snapshots — Take a snapshot before making significant changes. See Backup Strategy.
• Monitor your server — Set up alerts for disk usage and service health. See Server Metrics.

When to Contact Support

Contact support if:

• Rescue mode is not available or does not boot.
• The disk appears to have hardware-level issues.
• You are unable to repair the filesystem.
• The problem persists after all repair attempts.

What to Do Next

• Using the Web Console — Console access guide.
• Monitoring Server Performance — Prevent issues proactively.
• Backup Strategy — Protect against data loss.
• Slow Server Performance — Post-repair optimization.