Symptoms
When launching Plesk Installer ( /usr/local/psa/admin/bin/autoinstaller or /var/log/plesk/systemupdatestool.log on Linux )the following message is displayed
BUSY: Update operation was locked by another update process.
OR
Updates and Upgrades page returns the following error:
Can't connect to backend: No such file or directory
Resolution
Connect to the server using SSH and check the process:
# ps auxffww | grep autoinstaller
root 8405 0.0 2.0 200300 5372 pts/0 S+ 05:10 98:00 \\_ /usr/local/psa/admin/bin/autoinstaller
Get the PID and strace the process:
# strace -p $PID
If there is the following output:
...
poll([{fd=6, events=POLLIN|POLLPRI}], 1, 0) = 0 (Timeout)
poll([{fd=6, events=POLLIN|POLLPRI}], 1, 1000) = 0 (Timeout)
...
... this means the process is stuck. In that case, kill the process:
# kill -p $PID
Remove the /tmp/psa-installer.lock file if it exists or there was no process found.
Then run the autoinstaller again.