Hey. I'd have an additional question about subvols O:-)
Given the following setup: 5 | +--root (subvol, /) +-- mnt (dir) with the following done: - init 1 - remount,ro / (i.e. the subvol root) - mount /dev/btrfs-device /mnt (i.e. mount the top subvol at /mnt) The following happened: - / was ro-mounted (obviously, at least one thing that I had expected correctly) - /mnt was ro-mounted either (and the /mnt/root/ nested subvol then as well). => why is /mnt (i.e. the top level subvol) mounted ro?? => I would have expected that, since / (i.e. the subvol "root" is ro mounted), it's also ro mounted as the nested subvol below 5, i.e. my naive thinking was in terms of logic: "/ mounted ro" => "subvol root is mounted ro (everywhere)" => "thus /mnt/root/ is mounted ro as well" However, the later doesn't seem to be true, cause then I did: - remount,rw /mnt => now /mnt/*, including /mnt/root/* was rw moutned So I guess my assumption of subvols behaving more or less as if they'd be a fs (and thus mounted at one place ro => everywhere ro) is not true, is it? Do, ro,rw (and possibly others) instead only affect the respective mountpoint? And automatically any nested subvols of that mountpoint? So I could have basically: /mount-point1/subvol-a ; ro, noexec /mount-point2/subvol-a ; rw, compress=yes /root ; rw, compress=no /root/here/it/is/nested/subvol-a ; (no mountpoint) (with subvol-a being the same subvol) And when I write via mount-point1 I'd get an error, but via mount- point2 it works and in addition I get compression, while when writing via the /root mountpoint, where it is nested, I'd get the rw and compress=no from the "parent" mountpoint /root Does that sounds correct? It seems to make sense actually, though it's a bit unfamiliar... if I'm not correctly wrong, than e.g. in terms of ext* I cannot have the same fs mounted with different settings,... of course I cannot have it mounted twice at all, but speaking of bind mounts. So I guess, that when I'd do --bind mounts instead, I actually do get the "old" behaviour, i.e. when the source is ro, then the --bind mount's target is also forcibly ro. Still, one unclear thing, why got /mnt mounted ro very above? Thanks, Chris. btw: Not sure if I just missed it, but I guess the above should be more or less documented, showing people that mounting subvols (especially when mounting the same several times, either directly or as nested subvol) has these implications.
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