[systemd-devel] Antw: Re: Why does initrd-parse-etc.service re-start initrd-fs.target?

[Andrei Borzenkov]

09.12.2019 10:06, Ulrich Windl пишет:
>>
>> After real root is mounted daemon-reload re-runs fstab generator which
>> parses real root /etc/fstab and may pull mount points from it.
> 
> I wonder: Are there realistic cases when the fstab in initrd is newer than the
> fstab in the root file system?

It has nothing to do with being "newer". It allows managing initrd
filesystems in one place and avoids need to re-create initrd every time
you need additional filesystem.

> That would be the case where detecting a "new"
> fstab would fail. I didn't dig into the generators, but an alternative method
> to detect a file change would be to compare the size as well (as cheap as
> stat()), or to compare some checksum (requires some more extra code). I feel
> the generators should fix the issue, not the user (i.e. restart).
> 
>> Restarting initrd-fs.target will propagate start request to its (newly
>> created) dependent mount units. Otherwise there is no obvious way to
>> start them (without explicitly starting each).
> 
> I never liked the idea of generators and /etc/fstab.
> 

It fits perfectly into systemd design goal - start services *on boot*
once. Most problems with systemd stem from attempt to use it as "dynamic
service manager" which it is not. This discussion is example of it.