Let's say you are in my situation: you have bought recently a new mac, with Catalina (10.15) and you are switching from an older one that was supporting only High Sierra (10.13).

And you get this error when trying to do sudo port selfupdate.

How to start services in certain order with Systemd?
Have been reading a bunch of documentation to figure this one out.
By the way, this also includes the SysV startup scripts (which are called by systemd).

So, in this below example (real situation), I have Docker that needs ocfs2 filesystem which runs on top of DRBD.
Default startup configuration was not quite ok because docker almost always started first and ocfs2 was started in the same time with drbd and failed to mount the ocfs2 filesystem.

Ever wonder how to connect via ssh to a windows machine?
Of course there are other ways but I like this one better because it allows you to access the most powerful tool ever created for Windows: cygwin :)
So, here we go.

1. Run cygwin as administrator

Right click on the cygwin icon and select "Run as administrator".

If your DNS server no longer resolves non-authoritative queries (e.g. not your domains but yahoo.com or whatever.org) and you see this error in named logs:

If you need (as I do) multitab support in mintty, you can have it with the help of ... wait for it ... SCREEN!
It was always there but I haven't got this brilliant idea to use it.
Also, do not get fulled about the title as this works in any linux like environment.

Even if this tutorial includes only Linux, at least part of it may work on other UNIX like operating systems. You are free to test but as a golden rule: test it on TEST environment :).

I use Maintenance app to do some checks and cache cleanup from time to time. Today I got a message that my disk should be checked and repaired while in recovery.
So I did and I was surprised to find out this error while checking/repairing /: snap_metadata_val object: invalid extentref_tree_oid

Apparently this is related to local snapshots of time machine and one of them is in weird state indeed:

There are situations where you need to expose docker cli via a tcp port. For example when you use management tools like portainer.

On debian with systemd (stretch for example)

You need to add to ExecStart in /lib/systemd/system/docker.service: -H IP:2375:

You know how to pull and create custom images; do whatever with them.
But if you need the same custom image on multiple servers in your network, you will have to copy that image on them. Here comes docker registry: a local repository of your images.
And the installation of a local repository is done via (guess?) a container :).
Basically, all you have to do is to pull the registry image and run a container on top of it. As simple as that!

So I finally got a bit into docker because everybody is talking about it.
I will skip the installation part because it is not that difficult (easier than windows install actually: next, next, finish) and go straight to the interesting part: using docker commands.