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This script probably will not work on Linux systems with systemd (CentOS 7, Ubuntu 16.04, etc.). Systemd cages a process and it seems like sudo rules do not apply any more for a process started with systemd. We are investigating in this…

This script probably will not work on Linux systems with systemd (CentOS 7, Ubuntu 16.04, etc.). Systemd cages a process and it seems like sudo rules do not apply any more for a process started with systemd. We are investigating in this…

What is SELinux?

The Security-Enhanced Linux is an extension to the Linux Kernel, made by the NSA (National Security Agency). It implements Mandatory Access Controls (MAC), which allow an administrator to define, how applications and users can access resources on a system.

There is more detail in the SELinux Wki: https://selinuxproject.org/page/FAQ
… and the CentOS documentation: https://wiki.centos.org/HowTos/SELinux

Some distributions have it installed by default, but not active, some have it …

MySQL is well known and widely spread because of its philosophy of Keep it Simple (KISS).

We recently had the discussion that with newer releases also MySQL and MariaDB relational databases becomes more and more complicated.

One indication for this trend is the number of MySQL server system variables and status variables.

In the following tables and graphs we compare the different releases since MySQL version 4.0:

mysql> SHOW GLOBAL VARIABLES;
mysql> SHOW GLOBAL VARIABLES LIKE 'innodb%';
mysql> …

As you probably know MySQL is an Open Source product licensed under the GPL v2. The GPL grants you the right to not just read and understand the code of the product but also to use, modify AND redistribute the code as long as you follow the GPL rules.

This redistribution has happened in the past various times. But in the western hemisphere only 3 of these branches/forks of MySQL are of relevance for the majority of the MySQL users: Galera Cluster for MySQL, MariaDB (Server and Galera Cluster) and Percona …

FromDual has the pleasure to announce the release of the new version 1.0.0 of its popular Database Performance Monitor for MySQL, MariaDB, Galera Cluster and Percona Server fpmmm.

You can download fpmmm from here.

In the inconceivable case that you find a bug in fpmmm please report it to our Bug-tracker.

Any feedback, statements and testimonials are welcome as well! Please send them to feedback@fromdual.com.

This release contains various bug fixes and improvements. Further significant functionality has …

FromDual has the pleasure to announce the release of the new version 1.2.3 of the popular Backup and Recovery Manager for MySQL and MariaDB (fromdual_brman).

You can download the FromDual Backup and Recovery Manager from here.

In the inconceivable case that you find a bug in the Backup and Recovery Manager please report it to our Bugtracker or just send us an [email](mailto:contact@fromdual.com?Subject=Bug report for fromdual_brman).

Any feedback, statements and testimonials are welcome as well! Please send …

In our current project the customer wants to install and run multiple MySQL Enterprise Server 5.7 Instances on the same machine (yes, I know about virtualization (we run on kvm), containers, Docker, etc.). He wants to use Redhat Enterprise Linux (RHEL) 7 which brings the additional challenge of SystemD. So mysqld_multi is NOT an option any more.

We studied the MySQL documentation about the topic: Configuring Multiple MySQL Instances Using systemd. But to be honest: It was not really clear to me how to do …

I found out that we were wrong in this. We have taken RHEL6 MySQL RPM packages instead of RHEL7 packages. This is the reason why the installation was not smooth (but it worked) and why still old sysV init scripts were used.

I was informed that nowadays MySQL Enterprise Server and MySQL Community Server use both EditLine (since MySQL 5.6?).

The MySQL Server itself

The differences between the MySQL Community Server and the MySQL Enterprise Server 5.7 are as follows as claimed by Oracle:

• The license of the MySQL Server itself.
• Only MySQL Enterprise Edition has the Enterprise plugins (Thread Pool, PAM, Audit, etc.)
• Certifications and Indemnification support for the MySQL Enterprise Server.
• The MySQL Community Server statically links against yaSSL and readline vs MySQL Enterprise Server against OpenSSL and libedit. This restriction seems to be …

With 5.7.15 we had some strange installation errors which disappeared with 5.7.16. Further we found, that 5.7.15 still uses SysV init scripts and 5.7.16 has switched to SystemD…

Prepare the RPM repository server

Install the software to create a RPM repository server (on an Ubuntu web server):

shell> sudo apt-get install createrepo

Create the directory structures and initialize the repositories:

shell> sudo mkdir -p /var/www/html/repos/centos/7/os/x86_64
shell> sudo createrepo /var/www/html/repos/centos/7/os/x86_64/

Copy the MySQL Enterprise RPM packages to the repository:

shell> sudo cd /var/www/html/repos/centos/7/os/x86_64/
shell> sudo unzip -v …

If you have already Red Hat Enterprise Linux 7 (RHEL 7) or CentOS 7 in use you probably found out, that it is not that easy to install MySQL Enterprise Server because there are already pre-installed MariaDB 5.5 libraries:

shell> yum localinstall mysql-commercial-client-5.7.16-1.1.el7.x86_64.rpm mysql-commercial-libs-5.7.16-1.1.el7.x86_64.rpm mysql-commercial-server-5.7.16-1.1.el7.x86_64.rpm mysql-commercial-common-5.7.16-1.1.el7.x86_64.rpm
Loaded plugins: fastestmirror
Examining …

The same should apply for the MySQL 5.7 Community Server…

Somebody recently asked, what they had to do, if they wanted to move their InnoDB-Logfiles back to the datadir. As a challenge, the servers were part of a Galera Cluster.

My first thought was:

The problem is not the Galera Cluster itself, it is the rsync-SST (wsrep_sst_method = rsync) that could cause trouble and destroy your InnoDB-Logfiles, by simply overwriting or deleting them.

So I tried to confirm my thought and realised, I was wrong. This works anyway, because the node just takes the dataset from the …

Another idea we discussed (but does not fit to the problem) is lost space due to over-mounted directories. If you have some files in this directory they are not shown any more (= hidden) because they are over-mounted but they are still there an used space.

To look into an over-mounted directory to see the files in there the following recipe might help:

cd /mnt
touch 1 2 3
cd
mount /dev/sdd1 /mnt -> files are hidden now

mount --bind / /mnt2
ls /mnt2/mnt
1  2  3

For this phenomenon, the relevant documentation is here: deleting files. Close to the top, see this sentence:

The unlink function deletes the file name filename.
If this is a file’s sole name, the file itself is also deleted.
(Actually, if any process has the file open when this happens,
deletion is postponed until all processes have closed the file.)

This is the standard programming technique to ensure that temporary files are automatically cleaned up on a program or machine crash. Often this …

Today we had a very interesting phenomena at a customer. He complained that MySQL always get some errors of the following type:

[ERROR] mysqld: Sort aborted: Error writing file '/tmp/MYGbBrpA' (Errcode: 28 - No space left on device)

After a first investigation we found that df -h /tmp shows from time to time a full disk but we could not see any file with ls -la /tmp/MY*.

After some more investigation we found even the query from the Slow Query Log which was producing the same problem. It looked similar to …

FromDual has the pleasure to announce the release of the new version 0.10.6 of its popular Database Performance Monitor for MySQL, MariaDB, Galera Cluster and Percona Server fpmmm.

You can download fpmmm from here.

In the inconceivable case that you find a bug in fpmmm please report it to our Bug-tracker.

Any feedback, statements and testimonials are welcome as well! Please send them to feedback@fromdual.com.

This release contains various bug fixes and improvements. The previous release had some major bugs …