MySQL won't start after data dir move.

Question

I am running MySQL 5.1 on Ubuntu 10.04, and until recently, I used the default data dir location. Some other parts of the config file were tuned for performance, but the paths stayed default.

Recently, I started running out of space and decided to add another hard disk, mount it as /mysql and use it solely for MySQL data. So, I changed the paths, copied the old data dir into the new data dir and thought that would be the end of it.

Unfortunately, it wasn't - and it later turned out that apparmor was the issue, even though I updated the MySQL profile in apparmor to reflect the new path(s). After some messing about, disabling apparmor, the server would work and I was able to import the big database that is the original reason I needed more space.

Now, that was yesterday - the whole 200GB database was imported, keys were sorted and everything seemed fine until I tried to start the server today. Here's the error that I see in the log:

120913 13:53:38  InnoDB: Operating system error number 2 in a file operation.
InnoDB: The error means the system cannot find the path specified.
InnoDB: If you are installing InnoDB, remember that you must create
InnoDB: directories yourself, InnoDB does not create them.
InnoDB: File name /home/{my_username}/mysql/data/ibdata1
InnoDB: File operation call: 'create'.
InnoDB: Cannot continue operation.

Here's a few strange things with that:

a) I'm sudo-ed in as root, and I'm using the 'service mysql start' command to start it b) There's no mention of /home/{my_username}... path ANYWHERE in any of the configs.

I couldn't find any info or bug reports regarding this type of a problem. I don't even know what I would search for, since the problem can't really be explained in less than 2 paragraphs.

Further information: Manually setting innodb_data_home_dir eliminates the earlier problem, however, now I get this instead:

120913 14:08:06  InnoDB: Operating system error number 2 in a file operation.
InnoDB: The error means the system cannot find the path specified.
InnoDB: If you are installing InnoDB, remember that you must create
InnoDB: directories yourself, InnoDB does not create them.
InnoDB: File name /home/poplar/mysql/innodb-logs/ib_logfile0
InnoDB: File operation call: 'create'.
InnoDB: Cannot continue operation.

Now, there's no "poplar" user on this box, and I haven't got the faintest idea why would it want to be trying to put the log file there.

Answer 1

Well, it turned out that setting innodb_log_group_home_dir to the new MySQL data dir (where my log was before, and where it should default to anyway) did the trick.

The server now starts properly and all the data seems to be there.

I still don't know where it got the 'poplar' username as a good idea to try placing log files, but it could be some leftover (mis)configuration from AppArmor that wasn't cleanly re-set when I uninstalled it.