Category: Sysadmin

System administration is a special are of IT. It also has a special place in my heart. It is an interesting mixture of all the other disciplines, both common across the whole industry, and at the same time unique for each person, company, and geographical location. When I have something to say or share about system administration, I use this category.

Fedora 30

Fedora 30 has been released a few days ago. In the long list of changes, the most interesting to me are:

I’ve already upgraded my laptop to this version and everything seems to work as expected. The upgrade from Fedora 29 to Fedora 30 is easy:

# Install all the latest updates
dnf upgrade --refresh

# Install DNF plugin for system upgrades
dnf install dnf-plugin-system-upgrade

# Download all the necessary packages for Fedora 30
dnf system-upgrade download --releasever=30

# Reboot and start the upgrade of packages
dnf system-upgrade reboot

# Cleanup after successful upgrade
dnf system-upgrade clean

If this is not your first upgrade on the machine, it might also be a good idea to cleanup some of the installed packages BEFORE the upgrade, so that the process goes faster, skipping unnecessary downloads and upgrades. Here are a few suggestions:

# List all installed RPMs by size
rpm -qa --queryformat '%{size} %{name}\n' | sort -rn | less

# List all packages from earlier Fedora releases
rpm -qa | grep -i fc28

Zabbix in the Munich subway

Zabbix blog shares a very inspiring post “Zabbix in the subway. Munich Transport Corporation Case Study“, which shows how Zabbix is used for the monitoring of the trains and trams in Munich. Here are some implementation details to get you started:

Currently, there are 3796 devices monitored by the Zabbix server, which in turn houses the MySQL database and the web front-end. This server is operated virtually with 8 CPU’s and 32GB RAM supported by SAS storage system. 105818 items are queried by the Zabbix server from those devices, where 23820 triggers detect whether certain items deviate from their target state. This results in 298.48 NVPS with an average of approx. 7 people (actively) using the system concurrently. General overview:
* Each device inside a tram/subway is treated as a host and is monitored for availability.
* Each tram/subway is managed as a host group.
* Host groups are nested and organized by the tram/subway lines (using the host group nesting feature introduced in Zabbix 3.2).
* All devices depend on the connectivity of the MRCU (Mobile Radio Control Unit in subways) or LTE router (LTE G4 Connectivity in trams)
* Maps are automatically created for each tram/subway (using the Zabbix API).
* Maps use sub-maps to link to a specific tram/subway view.

There’s also a video from the Zabbix conference, presenting the case study.

StackOverflow: Developer Survey Results 2019

This year’s results for StackOverflow Developer Survey are in. This is probably the largest survey of IT professionals, with nearly 90,000 participating this year.

As always, there are plenty of insightful findings and correlations in the results. But one that I was somewhat glad to see was the attitude towards Blockchain technology.

While the mainstream media continues to confuse Blockchain with cryptocurrencies, technical people do understand the difference. And the majority (29.2% + 26.2% = 55.4%) of the survey respondents think it is useful for a variety of things outside of the cryptocurrency.

And with all the hype around cryptocurrencies and Blockchain, the majority of the organizations are not working with the technology just yet. Furthermore, of those that do work with Blockchain, the majority is NOT using it for the cryptocurrency.

That is pretty close to my mental picture of what’s going on.

How to disable IPv6 on CentOS / RHEL 7

Sometimes I miss the good old days …

Recently, I had an issue with one of the servers, where a bunch of services were attaching to IPv6 ports instead of the IPv4 ones. Rather than editing the configuration of each of these services, I wanted to simply disabled IPv6 on the machine.

In the old good days, things like these were easily done via the sysctl. I surely tried that option too, but it wasn’t enough. Turns out, the proper way these days is to do this via Grub, as per this blog post:

  1. Vim /etc/default/grub file
  2. Change: GRUB_CMDLINE_LINUX=”ipv6.disable=1 crashkernel=auto rhgb quiet”
  3. Regenerate and overwrite Grub config with: grub2-mkconfig -o /boot/grub2/grub.cfg
  4. Reboot.

That sounds a bit too excessive. But then again a reboot is also required for the proper disabling of SELinux, so I guess its’ fine.

Zabbix 4.2 is out!

Zabbix 4.2 has been released and it brings an impressive array of new features and improvements. Some of these are:

  • Built-in support of Prometheus data collection
  • Efficient high-frequency monitoring
  • Validation of collected data and error handling
  • Preprocessing data with JavaScript
  • Test preprocessing rules from UI
  • Test media type from Web UI
  • Support of TimescaleDB
  • Simplified tag management
  • More flexible auto-registration
  • Support for HTML emails
  • Animations and easy external services access on network maps
  • Extracting data from HTTP headers (like authentication tokens)
  • Non-destructive resizing and reordering of dashboard widgets
  • … and a lot more

If you were waiting for a good reason to upgrade – this is it!