SymptomsYou receive one of the following errors in Parallels Plesk Panel (PP) Control Panel:
"Domain ID is undefined."
"Client ID is undefined."
Or, you see an "Unable initialize session" error instead of the PP login page.
On PP for Windows servers, the error may be accompanied by the following warning:
CauseSuch errors usually occur if PP cannot create a session in $PRODUCT_ROOT_D/admin/sessions.
Please check that there is enough free disk space with these commands:
# df -h
# df -i
If disk space or inodes usage is at 100%, you can remove unnecessary files, such as different distributions, rotate log files in /var/log/, setup log rotation for domains in PP, etc.
Also, make sure that "$PRODUCT_ROOT_D/admin/sessions" has the correct permissions, for example:
# ls -ld /usr/local/psa/admin/sessions
drwxrwx--- 2 root psaadm 4096 Dec 12 15:09 /usr/local/psa/admin/sessions
The error is caused by a missing sessions folder in "%plesk_dir%\admin." To fix the issue, create a sessions folder in "%plesk_dir%\admin\."