Question: modification time for /usr and /etc

[peterbaouoft]

Hi,
It seems like for /usr on Atomic host, the modification time is canonicalized to epoch (1970), and this makes /usr always older than /etc.

However, to have system-sysusers to trigger automatically during boot time, /usr needs to be newer than /etc due to ConditionNeedsUpdate=/etc in the service file:

[rbao@unused-10-15-17-147 ~]$ cat /usr/lib/systemd/system/systemd-sysusers.service 
[Unit]
Description=Create System Users
Documentation=man:sysusers.d(5) man:systemd-sysusers.service(8)
DefaultDependencies=no
Conflicts=shutdown.target
After=systemd-remount-fs.service
Before=sysinit.target shutdown.target systemd-update-done.service
ConditionNeedsUpdate=/etc

 ................................................

Reading a bit from systemd code base, it seems like ConditionNeedsUpdate needs /usr to be strictly newer (i.e only > and not >=). See code and documentation. So I think canonicalize /etc to 1970 unfortunately would not be an option.

Any suggestions for changing modification time of /usr to be newer than /etc/ for systemd-sysusers to trigger? Or, we can have a conditional during rebase/deploy transactions that manually calls systemd-sysusers command if that also works... Thanks for your time =D.

NOTE: Related to #1376

[cgwalters]

Yeah, ConditionNeedsUpdate was designed for a dual-partition system, I'm not sure it was ever made to work for either classic or ostree systems. Perhaps the simplest is to have ostree write out /etc/.updated in the new deployment if it's built with systemd support.

[cgwalters]

To rephrase, this is ConditionNeedsUpdate not being compatible with OSTree. And now that I look it's based on timestamps of /etc/.updated and /usr/.updated, not timestamps of the directories. Hmm. So what we could do is teach ostree to write out /usr/.updated with the current timestamp (non-epoch), and then things should work?

[peterbaouoft]

And now that I look it's based on timestamps of /etc/.updated and /usr/.updated

Thanks for the response =D. For this part (/usr/.updated section), which part of the codebase were you looking at? I might miss the part for /usr/.updated section.. Were we looking at the same thing?

I was reading https://github.com/systemd/systemd/blob/master/src/shared/condition.c#L440-L447

if (lstat("/usr/", &usr) < 0)
                return true;

        /*
         * First, compare seconds as they are always accurate...
         */
if (usr.st_mtim.tv_sec != other.st_mtim.tv_sec)
        return usr.st_mtim.tv_sec > other.st_mtim.tv_sec;

[cgwalters]

You're right. OK if you don't mind let's refile this against ostree and discuss details there? I think Endless did some work here in the past...ah yep I found this endlessm/ostree@9ef61fd

[peterbaouoft]

You're right. OK if you don't mind let's refile this against ostree and discuss details there?

Sure :D.

ah yep I found this endlessm/ostree@9ef61fd

\o/

[peterbaouoft]

Close this in favor of ostreedev/ostree#1628