Plesk users (version 8.x up to 10.x as far as I've heared) are getting errors from the Watchdog module. Parallels is coming out with an update for this error in the future, but they can't tell when (yet). These errors occur on daily basis and are actually pretty easy to fix. You might have two errors (after each other), but this fix will solve them both.

The first error which occurs since the first of January 2011 is the following one:

ERROR: WDExc

Error occurred while processing database query: 'MySQL query failed: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'group by service_id, type, round(unix_timestamp(time) / 200, 0) having count(val' at line 3'

0: wdlib.php:1089

wd__db_query(string 'select service_id, type, unix_timestamp(min(time)) as min_time, unix_timestamp(max(time)) as max_time, avg(value) as avg

from module_watchdog_sys_stat where

group by service_id, type, round(unix_timestamp(time) / 200, 0) having count(value) > 1 limit 10000;')

1: pack-sysstats:63

pack_statistics(integer '200', boolean  false, boolean  false)

2: pack-sysstats:44

At the time being I was running Plesk 9.5.2. As Plesk 10 was out, I thought that would fix the problem. It kind of did, as I got a different error message:

/usr/local/psa/libexec/modules/watchdog/cp/pack-sysstats: line 1: ?php: No such file or directory

/usr/local/psa/libexec/modules/watchdog/cp/pack-sysstats: line 2: syntax error near unexpected token `"The file {$_SERVER['SCRIPT_FILENAME']} is part of Plesk 9 distribution. It cannot be run outside of Plesk 9 environment.\n"'

/usr/local/psa/libexec/modules/watchdog/cp/pack-sysstats: line 2: `    die("The file {$_SERVER['SCRIPT_FILENAME']} is part of Plesk 9 distribution. It cannot be run outside of Plesk 9 environment.\n");'

Fortunately I got some help through Twitter (@ParallelsPanel) and the Parallels Forum. The fix can be found here.

I've been upgrading Plesk today and yesterday. Although Plesk has a nice interface, it's not 100% clear in what happens. After some help on the FreeNode #plesk IRC channel and some cyberciti.biz pages, I've composed some details and commands to execute at the command line which can help when upgrading Plesk.

To Start Plesk

/etc/init.d/psa start

To Stop Plesk

/etc/init.d/psa stop

Upgrade through autoinstaller

/usr/local/psa/admin/bin/autoinstaller

Restart apache

/etc/init.d/httpd restart

Check the running processes.

The first column represents the owner. The second column contains the process id.

Source

ps aux | grep autoinstall

or

ps u

Killing a process

kill -9 [processid]

Backup an RPM database and rebuild it.

source 1

source 2

Remove any stale lock file

/bin/rm -f /var/lib/rpm/__db*

Back up the /var/lib/rpm directory

tar czvf $(hostname).rpmdatabase.tar.gz /var/lib/rpm

If your hostname is linux-server, it will save backup to a file called linux-server.rpmdatabase.tar.gz
Rebuild the rpm db

rpm --rebuilddb

Many thanks also go out to 'koor' who helped me at the #plesk IRC channel at FreeNode.

Collision of RPM files (RPM already exists)

When upgrading I encountered a collision of an RPM file which already existed. Because of that the upgrade could not proceed. A solution to that is presented here in the last post. It comes down to:

• Navigating to the folder which holds the rpm file (e.g. cd /root/psa/PSA_8.1.0/dist-rpm-RedHat-el3-i386/base)
• Forcing an update on the RPM. (e.g. rpm -U --force --nodeps psa-8.1.0-rhel3.build81061129.22.i586.rpm)

Running the updater after repairing the file will solve the problem.

SSH connection is refused
I had this problem once. After a little search I found this post. It's brilliant! From Plesk itself you start a cronjob (run it as root user) which (re)starts (or use restart instead of start) the ssh daemon. After that my problem was solved.

Virtual hosts
By default Plesk has a pre-defined 'behavior' of a domain. This includes some settings for PHP like safe mode and open basedir restrictions. By default these settings are stored in a file called 'httpd.include' in the folder

/var/www/vhosts/yourdomain.ext/conf/

You can edit this file to change the behavior of the domain, but changes in this file are just temporary. Once the file is reloaded your changes will be gone.
To permanently make changes you need to create or edit a file called 'vhost.conf' which is located in the same directory. When loading the httpd.include file, the webserver also checks if this vhost.conf file exists and if so, it includes it. How you can create this virtual host file can be found on this page.

Apache logs
The apache log files are located at

/var/log/httpd/

Webserver config
The webserver (httpd) config is located at

/etc/httpd/conf/httpd.conf