Gentoo Archives: gentoo-dev

From: Michael Orlitzky <mjo@g.o>
To: gentoo-dev@l.g.o
Subject: Re: [gentoo-dev] OT: persistence of directories under /var/cache
Date: Fri, 26 Apr 2019 12:06:09
In Reply to: Re: [gentoo-dev] What's going on with the tmpfiles eclasses? by "Michał Górny"
1 On 4/26/19 12:53 AM, Michał Górny wrote:
2 >
3 > No. tmpfiles is also used for programs started directly by user, such
4 > as eix.
5 >
7 This configuration is buggy to begin with: if I run eix-update as my
8 user, then the permissions on the files it creates under /var/cache/eix
9 are wrong (mjo:mjo, mode 664). If I run eix as root and it drops
10 privileges, then the permissions on the files it creates are correct
11 (portage:portage, mode 664). But when I run eix as root, eix can create
12 /var/cache/eix itself! It doesn't need the tmpfiles entry in the
13 scenario that works. Maybe a setgid bit could make sense of things, but
14 the simplest solution is probably best: a per-user cache.
16 Regardless of the particulars of eix, I'm a lot skeptical of treating
17 directories under /var/cache as temporary in the first place. It leads
18 to problems just like this one, where a non-root process can't be sure
19 that its cache directory will exist and have the correct permissions. In
20 this case we've solved the problem by requiring either OpenRC or
21 systemd, but that's not a good answer.
23 We would be much better off if the ebuild could create that directory
24 with the correct permissions once, and know that it will persist. The
25 FHS is ambiguous here:
29 It calls out files specifically,
31 Files located under /var/cache may be expired in an application
32 specific manner, by the system administrator, or both. The application
33 must always be able to recover from manual deletion of these files
34 (generally because of a disk space shortage). No other requirements
35 are made on the data format of the cache directories.
37 The fact that we can't track the directory /var/cache/eix without a file
38 at /var/cache/eix/.keep is something else to worry about, but that's a
39 problem we've caused ourselves and one worth ignoring if it saves us
40 enough trouble.