Category: Linux

Linux is my primary operating system. I used it on the servers, desktops, laptops, netbooks, and even mobile phones since approximately 1997. I’ve tried a number of distributions over the years, and even created a couple myself. I still look around sometimes to see what others are up to. But most of my machines are running some sort of Red Hat – either a quick and easy Fedora Linux, or a stable and secure Red Hat Enterprise Server, or a cheaper CentOS alternative.

And while by now I am very comfortable in the Linux environment (both graphical and command line), I still discover a lot of new and interesting things about it. When I come across something worthy, I usually share it with the rest of the Open Software world, using this category.

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.

Configuring HA Kubernetes cluster on bare metal servers

Alexey Nizhegolenko has an excellent 3-part series of articles that cover the setup of Kubernetes on the bare metal servers. Here are the parts:

If that’s not a hand-holding walk-through guide, then I don’t know what is.

Unix History Repository

Evolution of unix-history-repo (Gource Visualization) video shows how the UNIX operating system was born and how it matured over time. The video is based on this GitHub repository, which combines the following:

The project has achieved its major goal with the establishment of a continuous timeline from 1970 until today. The repository contains:
– snapshots of PDP-7, V1, V2, V3, V4, V5, V6, and V7 Research Edition,
– Unix/32V,
– all available BSD releases,
– the CSRG SCCS history,
– two releases of 386BSD,
– the 386BSD patchkit,
– the FreeBSD 1.0 to 1.1.5 CVS history,
– an import of the FreeBSD repository starting from its initial imports that led to FreeBSD 2.0, and
– the current FreeBSD repository.
The files appear to be added in the repository in chronological order according to their modification time, and large parts of the source code have been attributed to their actual authors.

This is mind-blowing! So much work, so many people, so little recognition. The world wouldn’t be the same without all that, and yet the masses think that Steve Jobs or Bill Gates were the greatest computer geniuses in the history of mankind. Sad…

But the video is beautiful. It desperately needs some music though.

Programmer migration patterns

“Programmer migration patterns” is an interesting attempt to identify where programmers start and how move from one programming language to another. This is not precise science, obviously. But I have to say that I mostly agree with the findings.

The first language that I learned (back in school) was BASIC, which then gave me some legs with Visual Basic later in college. Also in college, I’ve learned assembler, C, and Pascal, which guided me to some amateur and professional development with Delphi.

Soon after that I discovered Linux, which meant shell scripting. I played with awk, but I didn’t have to dive deep, as Perl was already available. Perl was probably my first true programming language, which I learned outside of school and college, and which I have been using for years to build all kinds of things. I still love Perl dearly, but the last few years I have been mostly using PHP, with some occasional Python.

JavaScript, however, is where I draw the line. I’ve been scarred by JavaScript back in the 90s, so I can’t force myself to go back. And then again, I don’t really have to. I’ll leave JavaScript, TypeScript, and node.js for the younger generations.

Let the source be with you!

Fedora Linux : Change user icon in GDM login

In general, I’m pretty happy with my desktop setup. I use MATE with i3 on my Fedora Linux laptop for quite some time now, and it works well.

However, there was one annoying tidbit that I decided to fix today – my user icon on the login screen. I remember that I used to have it at some point, but it disappeared during some upgrade a few month ago.

The login screen is managed by Gnome Display Manager (GDM). In previous versions, you could easily customize the user icon via either some GUI tools for users and groups, or by simply dropping your icon into ~/.face file, in, preferably, PNG format, and GDM would pick it up just fine. Turns out, not anymore.

It took me a few Google searches to find the solution, so I’m sharing it here (just replace ‘leonid’ everywhere with your own username):

# Copy the user icon file
sudo cp /home/leonid/.face /usr/share/pixaps/faces/leonid.png
# Edit user settings file and add the following line:
# Icon=/usr/share/pixaps/faces/leonid.png
sudo vim /var/lib/AccountsService/users/leonid
# Logging out is not enough, so just ...
reboot

Once your system restarts, you should see the proper user icon on the login screen.