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Have you ever tried to kill a query, but rather than just go away, it remained among the running ones for an extended period of time? Or perhaps you have noticed some threads makred with killed showing up from time to time and not actually dying. What are these zombies? Why does MySQL sometimes seem to fail to terminate queries quickly? Is there any way to force the kill command to actually work instantaneously? This article sheds some light on it.

No space left on device - this can happen to anyone. Sooner or later you may face the situation where a database either has already or is only minutes away from running out of disk space. What many people do in such cases, they just start looking for semi-random things to remove - perhaps a backup, a few older log files, or pretty much anything that seems redundant. However this means acting under a lot of stress and without much thinking, so it would be great if there was a possibility to avoid that. Often there is. Or what if there isn't anything to remove?

Security-Enhanced Linux or SELinux is a Linux kernel feature that provides a mechanism for supporting access control security policies. It enables a system administrator to create an extra set of rules that define allowed operations for programs even after the standard controls are checked. In other words, SELinux can help improving system security by restricting access of an application to only a few resources it actually needs, which makes it more difficult for an attacker to gain access to the entire system through exploiting any possible vulnerabilities in the application. However as rarely anything in life is free, is there any price we have to pay to use SELinux on a MySQL server?

A few days ago I showed a quick way to extract one table form a mysqldump output. Here is a more complete version which supports extracting either a full schema or a table from the specified schema. If full schema is being extracted, the script also looks for any associated views and routines.

Using mysqldump is a quick way to do backups, although usually limited to only smaller databases - perhaps up to a few gigabytes large. It is still a fairly popular solution as majority of databases aren't even that big. Also phpMyAdmin provides a variant of mysqldump format through its Export function. Everything works well for plain dump and restore, but in certain situations it is necessary to restore only a single table. With all data being in a single text file, it may not be a trivial task. Here is how I deal with the problem.