TIL how to debug a broken nextcloud login (again)

The symptoms of this problem were the same as the ones I described in TIL how to debug a broken nextcloud login .

Problem

Phone and Mac apps stopped syncing data with the Nextcloud instance. In my browser I could access the login page, but after entering the details I was being sent back to the same login page without any error message.

Investigation

Last time the issue was caused by excessive logging. However, I reduced the loglevel in the nextcloud config, so this was not the issue here. I am no expert in web admin, PHP, or nextcloud, so I used Claude 3.5 to pair on debugging:

I can’t say that the suggestions worked right away, but they put me on the right path and helped me with some useful debugging commands.

The command

df -h

showed me that I didn’t have any free space. While the command

du -sh /var/www/nextcloud/data/*

indicated that in nextcloud a lot of space was occupied by old file versions and deleted files from the nextcloud file sync.

Solution

You can use the nextcloud console occ (ownCloud Console) tool to run maintenance tasks on the nextcloud instance.

The command

sudo -u www-data php /var/www/nextcloud/occ list

lists all available commands.

A couple of clean up commands to remove old file versions and files in the trashbin worked for me:

# Check Nextcloud trashbin size
sudo -u www-data php /var/www/nextcloud/occ trashbin:cleanup --all-users

# Clean up file versions
sudo -u www-data php /var/www/nextcloud/occ versions:cleanup

# Clear Nextcloud cache:
sudo -u www-data php /var/www/nextcloud/occ cache:clear

This freed up enough space for nextcloud to work again.

Unfortunately, the occ commands didn’t work right away because there was apparently not enough space to run any of them. Each one returned the same error message:

fwrite(): write of 4963 bytes failed with errno=28 No space left on device 

So I first had to free up a few hundred megabytes:

• Clear local repository of retrieved package files:

  sudo apt-get clean
  

• Remove old log files:

  sudo find /var/log -type f -name "*.gz" -delete
  sudo find /var/log -type f -name "*.1" -delete
  sudo truncate -s 0 /var/log/*.log
  

• Remove temporary files:

  sudo rm -rf /tmp/*
  

This cleared enough space to run the occ commands.