Re: [ptxdist] Resend: Home dir fixup for root in systemd

[Michael Olbrich <m.olbrich@pengutronix.de>]

Hi,

On Tue, Jul 26, 2016 at 04:00:34PM +0200, David Jander wrote:
> On Tue, 26 Jul 2016 15:19:59 +0200
> Guillermo Rodriguez Garcia <guille.rodriguez@gmail.com> wrote:
> 
> > Wouldn't it be easier to either use a custom /etc/passwd, or create a /root
> > dir in the filesystem ? That sounds better than patching systemd.
> 
> Maybe it would be better to change the default /etc/passwd (and everywhere
> else) in ptxdist then...
> 
> The problem is that what /etc/passwd says is mandatory. The home directory has
> a special meaning to the user. You can get to the home directory via $HOME
> passed in the environment, or via the NS-switch (getent) lookup. They are
> supposed to be the same.
> systemd has hardcoded defaults in source-code, which by definition is ugly as
> hell, but the reason is clearly to avoid potentially expensive, blocking
> NSS-lookups in the early boot stages, so it is understandable. It would be a
> lot better if there was some configuration setting read from a file I guess,
> but alas.
> On PTXdist now (with the default, shipped /etc/passwd), a user logging in as
> "root" via, say a serial console getty, will have a different $HOME than a
> systemd service started with User=root. This is bad, and can potentially do
> funny things people will not like.
> To solve the problem, there are really only two options AFAICS:
> 
>  1.- Change PTXdist and all places in it that assume the $HOME=/home for root.
>  No idea how many places that are, nor how many users already depend on this
>  historic assumption.
> 
> or
> 
>  2.- Patch systemd to adapt to the reality of PTXdist.
> 
> I agree that option 1 is probably better if PTXdist is more or less the only
> place on earth left where $HOME != /root for uid=0. Historically on Unix it
> used to be "/", but that is just way too ugly (guess where the name "root"
> came from?).
> 
> Using a custom /etc/passwd is not an option, because the default PTXdist stays
> broken this way.
> 
> Creating a /root dir is also broken, because like I explained above, the root
> user will become schizophrenic when logging in and running services from
> systemd alternately. Think about a user logging in, starting a tool that
> writes a config files to ~/.bla, and then configuring the same tool to run as a
> system service. I would (did!) get slightly mad when finding the tool to run
> with a totally different configuration in the latter case.

Unless someone comes up with a really good reason, then I think we should go
with option 2. I have actually considered making the change in the past
just to be consistent. But I never got around to do it.
I didn't notice this problem, probably because my rootfs is usually
read-only, and /root and /home are both empty.

It would be great if some more people would speak up. Such a change can
potentially break things, so I'd like to know what others are thinking.

Michael

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