The Jenkins admin console should be able to run all the time, even when the Master node is offline. So, you’re facing this problem because Jenkins ran out of disk space.
To check this,
- Go to Jenkins > Manage Jenkins > Manage nodes
- Check if the master node is offline. It may report that the master node is out of disk space.
- If not, then check the number of executors allocated, it is probably set to zero. Increase the number of executors and this will fix the problem.