“MySQL Server has gone away” is a cryptic error that can be hard to troubleshoot (look at all the various responses on Stack Overflow!) Many problems can cause this error; I would like to document one specific case. In this example, the client is a PHP app using the Phalcon framework: [Mon, 09 Apr 18 […]
General error: 2006 MySQL server has gone away Read More »
When you run yum upgrade on a CentOS/RedHat 7 instance, you will be upgraded to 7.4. If you have a FreeRADIUS server, you will be upgraded from version 2 to 3, and your server will likely stop authenticating! Good times! Fortunately, the solution was not complicated for us, because we had good documentation. Symptoms Your
Warning: CentOS/RedHat 7.4 installs FreeRADIUS 3 with breaking changes Read More »
It can confusing when you have multiple persistent disks on an instance running on Google Compute Engine. For example, a server may have separate disks for the filesystem root, MySQL data, logs, and /tmp. Once you’ve created the Compute Engine disks and attached each one to the instance, how do you know which Compute Engine
Managing persistent disks on Google Compute Engine Read More »
Assumption: You have SELinux Enforcing on your database server. If you’re still solving problems by permanently setting SELinux to Permissive, I don’t think you can really call yourself an IT professional. Here are the commands to set the SELinux context of all text MySQL log files to var_log_t so that they can be rotated by
MySQL/MariaDB, logrotate, and SELinux Read More »
Summary: The Synology DS 1515+ is a capable little NAS with a large feature set, but it has some software reliability issues and limited technical support. Hardware The DS1515+ is a compact unit that feels sturdy. It holds five 2.5″ or 3.5″ drives, and 3.5″ drives can be installed without any tools. You will need
Synology DiskStation DS1515+ Review Read More »
On RedHat and CentOS 6 and 7, anacron generates syslog messages that are mangled when they are forwarded by rsyslog. I found the cause and a solution in a comment by Tomas Heinrich on this old Fedora bug. Sadly, that bug was closed instead of getting fixed, probably because Fedora is oriented toward desktop users
anacron run-parts generates invalid or malformed syslog messages Read More »
If you are a Linux or OS X power user, then you’re used to having all the necessary tools built into your OS. When you log into a Windows system (What! No command line?) you may feel lost. These tools and shortcuts will help you be productive on Windows systems. Windows Shortcuts Alt-x is a
Making Windows work for Linux and OS X admins Read More »
SSSD (System Security Services Daemon) allows Linux systems (specifically, Red Hat, CentOS, and Fedora) to verify identity and authenticate against remote resources. If you have a CentOS or Red Hat enterprise system, and you need to authenticate against a domain controller such as FreeIPA or Active Directory, SSSD is the way to go. I use
Troubleshooting SSSD, realm, kerberos, and SSH Read More »
LVM2 (Logical Volume Management) is pretty amazing, but when something goes wrong, it’s not easy to troubleshoot. This is not the fault of the tools, but a reflection that LVM is relatively new in Linux, and not widely understood. What I Tried to Do I tried to increase the size of a logical volume with the lvextend
LVM device-mapper: reload ioctl failed: Invalid argument Read More »
My last post showed how to monitor networked devices with SNMP. You could try to remember to manually check the status of things periodically, but that would be missing the point of computers. Instead, automate your monitoring with Nagios, a web-based monitoring tool for Linux that automates the process of actively querying devices and doing
Monitoring with SNMP, Part 3: Automate active monitoring with Nagios Read More »