Date: Fri, 22 Nov 2019 09:09:52 +0100 From: Borja Marcos <borjam@sarenet.es> To: Martin Simmons <martin@lispworks.com> Cc: jbe-mlist@magnetkern.de, freebsd-fs@freebsd.org Subject: Re: ZFS snapdir readability (Crosspost) OT: mount -t zfs for snapshots Message-ID: <B708E4EB-0387-47B2-B03F-A2134A3F3169@sarenet.es> In-Reply-To: <201911211630.xALGUT5Z010705@higson.cam.lispworks.com> References: <20191107004635.c6d2e7d464d3d556a0d87465@magnetkern.de> <CAOtMX2huHZcXHH%2B=3Bx7hX_p9udJ2acOX%2BZL8vW=pjqbe6mOAA@mail.gmail.com> <e2eecef7-21b6-0ff2-b259-71421b7d097c@sentex.net> <9B22AD46-BE87-4305-9638-74D23AD4C8CA@sarenet.es> <cfcc12dd-e9eb-5a98-a031-ab18436a2dd3@sentex.net> <261FE331-EC5C-48C8-9249-9BCBF887CE38@sarenet.es> <913f7040-6e38-452d-6187-e17fae63b652@sentex.net> <20191120144041.7f916360dc0c69bf509c9bd1@magnetkern.de> <AEF4CA02-36B3-42FC-BE92-14DF0AF99540@sarenet.es> <20191120163437.691abd369ab9c0a6d7d45ff2@magnetkern.de> <CF38B478-3638-4C18-B69F-E589DE9BBB95@sarenet.es> <20191120175803.03401c3316fe756cc46f79f1@magnetkern.de> <3C5DC6DD-C44B-41EE-B7AB-6D8F94E43174@sarenet.es> <201911211259.xALCxShX008743@higson.cam.lispworks.com> <462E2C53-2490-4B8C-BB54-BCE8B75BAEB0@sarenet.es> <201911211630.xALGUT5Z010705@higson.cam.lispworks.com>
next in thread | previous in thread | raw e-mail | index | archive | help
> On 21 Nov 2019, at 17:30, Martin Simmons <martin@lispworks.com> wrote: > >> >> I’ve never seen that and, indeed, on FreeBSD 12.1 it’s not possible. Or I am terribly >> sloppy today! >> >> Did I miss anything? Is it a new ZFS on Linux feature? >> >> >> root@micro1:~ # mount -t zfs -o ro pool/dataset@snapshot /mnt >> mount: unpul/wwwnfsen@antesinst: Device busy >> root@micro1:~ # > > It looks like unpul/wwwnfsen@antesinst is already mounted -- probably in .zfs :-) (This is a bit of off-topic now, the behavior of mount -t zfs) Yep, it’s only uglier! Whenever you access any of the directories below .zfs/snapshot the snapshot is automagically mounted. It’s also sort of invisible except when you run “mount -v”. In that case those snapshot mounts are visible. You can also unmount them. But it’s rather opaque. Auto mounted snapshots are invisible to mount(8) unless the -v option is used, regardless of the status of the snapdir property. However, when you mount them explicitly they are visible. Anyway, was this intended or is it a side effect of the general behavior of mount? I see it’s not documented on the FreeBSD Manual, which only mentions mounting snapshots as clones. Which, as far as I know, is consistent with the original ZFS design. Thank you for all the explanations, I was convinced that cloning was the only way to mount a ZFS snapshot. Borja.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?B708E4EB-0387-47B2-B03F-A2134A3F3169>