[systemd-devel] Using timedatectl on a readonly rootfile system using mender

[Shravan Singh]

Hello Lennart,

Can you help me in understanding why this push was rejected?
*Make timedatectl nicely work with read-only filesystems #8277 *
If there is some major issue. I would like to take this opportunity to make
it right and submit it again


Regards,
Shravan Singh
(239) 243-0838

Blue Sparq, Inc.
928 NE 24th Lane unit 4 and 5.
Cape Coral, FL 33993

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On Fri, Sep 4, 2020 at 11:27 AM Lennart Poettering <lennart at poettering.net>
wrote:

> On Do, 20.08.20 14:22, Shravan Singh (shravan at bluesparq.com) wrote:
>
> > But no one is telling how to resolve my issue with a read-only
> > rootfs.
>
> There's no concept for having some files in /etc writable and others
> not. And you cannot use symlinking for this, nor bind mounts, since
> config files in /etc are usually updated atomically, i.e. new versions
> written in full into temporary files and then moved into place
> atomically so that you either see the old or the new but never
> anything half-written. This means that the dir of the file to update
> needs to be writable and that the old inode goes away entirely on
> update instead of being updated.
>
> I must say I see little point in having "etc mostly read-only"
> though. I mean, either your config is entirely read-only or it
> isn't. If it is read-only /etc being read-only is not a problem. If it
> can be modified then make /etc the source of truth for it and
> writable, and drop everything else from it, so that it only contains
> the writable data you care about. A lot of software these days falls
> back to fallback settings below /usr somewhere if their config files
> in /etc don#t exist, and for the stuff that doesn't work like this,
> move it over and symlink it from /etc (you can create those symlinks
> with tmpfiles.d factory options).
>
> > There are other files which can be overwritten in /etc that are linked
> to a
> > file in /run directory for eg /etc/resolv.conf file.
>
> Well, that file is quite different, resolve.conf is historically was
> configuraiton but today is more state than configuraiton, i.e. it is
> usually configured dynamically via DHCP or so. Hence people started to
> manage it in /run and leave /etc/resolv.conf only as a compat symlink
> in place, if you so will.
>
> > Then why not /etc/localtime. Why is localtime guarded so much
> > I refuse to believe that I am the only person facing this problem. But I
> > did find some leads now. Will keep you posted
>
> /etc/localtime is generally considered to be configuration and not
> state, hence people are typically fine with leaving it in /etc, since
> that's where persistant configuration is supposed to be.
>
> I am sorry, but /etc on Linux is a single directory, and you can only
> cleanly choose between all configuration read only or none, there's no
> nice way for a middle ground. Sorry.
>
> Lennart
>
> --
> Lennart Poettering, Berlin
>
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