(RHEL-6223) fstab-generator: Chase symlinks where possible (#6293) #146
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This has a long history; see see 5261ba9 which originally introduced the behavior. Unfortunately that commit doesn't include any rationale, but IIRC the basic issue is that systemd wants to model the real mount state as units, and symlinks make canonicalization much more difficult. At the same time, on a RHEL6 system (upstart), one can make e.g. `/home` a symlink, and things work as well as they always did; but one doesn't have access to the sophistication of mount units (dependencies, introspection, etc.) Supporting symlinks here will hence make it easier for people to do upgrades to RHEL7 and beyond. The `/home` as symlink case also appears prominently for OSTree; see https://ostree.readthedocs.io/en/latest/manual/adapting-existing/ Further work has landed in the nspawn case for this; see e.g. d944dc9 A basic limitation with doing this in the fstab generator (and that I hit while doing some testing) is that we obviously can't chase symlinks into mounts, since the generator runs early before mounts. Or at least - doing so would require multiple passes over the fstab data (as well as looking at existing mount units), and potentially doing multi-phase generation. I'm not sure it's worth doing that without a real world use case. For now, this will fix at least the OSTree + `/home` <https://bugzilla.redhat.com/show_bug.cgi?id=1382873> case mentioned above, and in general anyone who for whatever reason has symlinks in their `/etc/fstab`. (cherry picked from commit 634735b) Resolves: RHEL-6223
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This has a long history; see see 5261ba9 which originally introduced the behavior. Unfortunately that commit doesn't include any rationale, but IIRC the basic issue is that systemd wants to model the real mount state as units, and symlinks make canonicalization much more difficult.
At the same time, on a RHEL6 system (upstart), one can make e.g.
/homea symlink, and things work as well as they always did; but one doesn't have access to the sophistication of mount units (dependencies, introspection, etc.) Supporting symlinks here will hence make it easier for people to do upgrades to RHEL7 and beyond.The
/homeas symlink case also appears prominently for OSTree; see https://ostree.readthedocs.io/en/latest/manual/adapting-existing/Further work has landed in the nspawn case for this; see e.g. d944dc9
A basic limitation with doing this in the fstab generator (and that I hit while doing some testing) is that we obviously can't chase symlinks into mounts, since the generator runs early before mounts. Or at least - doing so would require multiple passes over the fstab data (as well as looking at existing mount units), and potentially doing multi-phase generation. I'm not sure it's worth doing that without a real world use case. For now, this will fix at least the OSTree +
/homehttps://bugzilla.redhat.com/show_bug.cgi?id=1382873 case mentioned above, and in general anyone who for whatever reason has symlinks in their/etc/fstab.(cherry picked from commit 634735b)
Resolves: RHEL-6223