Re: finding root filesystem of a subvolume?
On 2017-08-23 14:07, Austin S. Hemmelgarn wrote: > On 2017-08-22 13:41, Peter Grandi wrote: > [ ... ] >> This stupid point relies on ignoring that it is not mandatory to >> mount the main volume, and that therefore "There is no fixed >> relationship between the root directory inode of a subvolume and >> the root directory inode of any other subvolume or the main >> volume", because the "root directory inode" of the "main volume" >> may not be mounted at all. >> >> This stupid point also relies on ignoring that subvolumes can be >> mounted *also* under another directory, even if the main volume >> is mounted somewhere else. Suppose that the following applies: >> >> subvol=5 /local >> subvol=383 /local/.backup/home >> subvol=383 /mnt/home-backup >> >> and you are given the mountpoint '/mnt/home-backup', how can you >> find the main volume mountpoint '/local' from that?Assuming >> /mnt/home-backup is mounted and visible in /proc/mounts (your > explanation requires it was either mounted directly via a subvol option > or indirectly via a bind mount), then the following generic method works > (and should always work on a modern kernel): > 1. Find it in /proc/mounts or the output of `mount` run without any > arguments. > 2. If the mount type is 'bind', the device field will point to the > source directory. Using any method you like, figure out what the actual > mount point that is under is, and repeat from step one with that mount > point. > 3. If the mount type is 'btrfs', and 'subvolid=5' is present in the > mount options (this gets added automatically on any recent kernel), you > just found the top level subvolume. > 4. If the mount type is 'btrfs', and 'subvolid=5' is not present in the > mount options, scan /proc/mounts for other entries with the same device > value (this is going to be consistent). > 5. If another entry does exist, and has 'subvolid=5' in the mount > options, that's the top level subvolume. > 6. If other entries exist, but 'subvolid=5' not in the mount options for > any of them, or no other entries exist, the top level volume isn't > mounted, and you can view it by mounting the device with 'subvolid=5'. > > In the event that you need to know where the next higher level subvolume > is mounted instead of the root subvolume for the volume, you can use the > same method, but add the following after step two to figure out what > subvolid to look for: > 2b. Run `btrfs subvol show` on the mount point (it by definition has to > be a subvolume because it's mounted and it's not a bind mount in > userspace). Find the 'Top level ID' (note that this just points to the > next higher subvolume, not the root subvolume) value in the output, and > use that instead of 5 when looking for 'subvolid=' options. In order to have a complete view of all mounts, this is what btrbk does here (which basically matches Austins explanation): 1. Buld a complete tree from: # btrfs subvolume list -a -u /mnt/home-backup 2. Correlate all subvolume ID's with mount points (second column) and "subvolid=" from mount options: # cat /proc/self/mounts Now you have a complete view of all mounts. In order to query a given subvolume, fetch "Subvolume ID" (or "UUID") from: # btrfs subvolume show /local/.backup/home see: https://github.com/digint/btrbk/blob/v0.25.1/btrbk (I apologize that Github has broken display of perl source files at the time being...) -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On 2017-08-22 13:41, Peter Grandi wrote: [ ... ] There is no fixed relationship between the root directory inode of a subvolume and the root directory inode of any other subvolume or the main volume. Actually, there is, because it's inherently rooted in the hierarchy of the volume itself. That root inode for the subvolume is anchored somewhere under the next higher subvolume. This stupid point relies on ignoring that it is not mandatory to mount the main volume, and that therefore "There is no fixed relationship between the root directory inode of a subvolume and the root directory inode of any other subvolume or the main volume", because the "root directory inode" of the "main volume" may not be mounted at all. This stupid point also relies on ignoring that subvolumes can be mounted *also* under another directory, even if the main volume is mounted somewhere else. Suppose that the following applies: subvol=5 /local subvol=383 /local/.backup/home subvol=383 /mnt/home-backup and you are given the mountpoint '/mnt/home-backup', how can you find the main volume mountpoint '/local' from that?Assuming /mnt/home-backup is mounted and visible in /proc/mounts (your explanation requires it was either mounted directly via a subvol option or indirectly via a bind mount), then the following generic method works (and should always work on a modern kernel): 1. Find it in /proc/mounts or the output of `mount` run without any arguments. 2. If the mount type is 'bind', the device field will point to the source directory. Using any method you like, figure out what the actual mount point that is under is, and repeat from step one with that mount point. 3. If the mount type is 'btrfs', and 'subvolid=5' is present in the mount options (this gets added automatically on any recent kernel), you just found the top level subvolume. 4. If the mount type is 'btrfs', and 'subvolid=5' is not present in the mount options, scan /proc/mounts for other entries with the same device value (this is going to be consistent). 5. If another entry does exist, and has 'subvolid=5' in the mount options, that's the top level subvolume. 6. If other entries exist, but 'subvolid=5' not in the mount options for any of them, or no other entries exist, the top level volume isn't mounted, and you can view it by mounting the device with 'subvolid=5'. In the event that you need to know where the next higher level subvolume is mounted instead of the root subvolume for the volume, you can use the same method, but add the following after step two to figure out what subvolid to look for: 2b. Run `btrfs subvol show` on the mount point (it by definition has to be a subvolume because it's mounted and it's not a bind mount in userspace). Find the 'Top level ID' (note that this just points to the next higher subvolume, not the root subvolume) value in the output, and use that instead of 5 when looking for 'subvolid=' options. Please explain how '/mnt/home-backup' is indeed "inherently rooted in the hierarchy of the volume itself", because there is always a "fixed relationship between the root directory inode of a subvolume and the root directory inode of any other subvolume or the main volume". You did one of three things to mount that: 1. You used a bind mount directly. In this case, you're not changing the relation at all of the subvolume (which is technically not what's mounted in this case because a bind mount operates at the VFS layer and knows nothing about subvolumes) and it's parent subvolumes. 2. You mounted using 'subvol=.backup/home'. This in and of itself should pretty concisely explain that there is a hierarchical relationship between subvolumes. That path indicates the path in the hierarchy of the volume itself used to access the subvolume. 3. You mounted using 'subvolid=383'. This is the only case where there isn't a hierarchical relationship, and just uses the tree ID to reference the subvolume. This is the only case where there isn't some direct reference to the parent subvolume. Note also that this relation is not inherent to the subvolume, but to it's parent. Just like a symbolic link, the reference is in the containing object, not the referenced object (although subvolumes do store info about what their parent subvolume is). [ ... ] Again, it does, it's just not inherently exposed to userspace unless you mount the top-level subvolume (subvolid=5 and/or subvol=/ in mount options). This extra stupid point is based on ignoring that to "mount the top-level subvolume" relies on knowing already which one is the "top-level subvolume", which is begging the question. You have information in /proc/mounts as to what is mounted. Trace your particular path up to that, and then mount the indicated block device with `-o subvolid=5`. The subvolume with ID 5 is _ALWAYS_ the top level subvolume for the volume, that's inherently hard coded in the filesystem format, so if that's
Re: finding root filesystem of a subvolume?
[ ... ] >> There is no fixed relationship between the root directory >> inode of a subvolume and the root directory inode of any >> other subvolume or the main volume. > Actually, there is, because it's inherently rooted in the > hierarchy of the volume itself. That root inode for the > subvolume is anchored somewhere under the next higher > subvolume. This stupid point relies on ignoring that it is not mandatory to mount the main volume, and that therefore "There is no fixed relationship between the root directory inode of a subvolume and the root directory inode of any other subvolume or the main volume", because the "root directory inode" of the "main volume" may not be mounted at all. This stupid point also relies on ignoring that subvolumes can be mounted *also* under another directory, even if the main volume is mounted somewhere else. Suppose that the following applies: subvol=5 /local subvol=383/local/.backup/home subvol=383/mnt/home-backup and you are given the mountpoint '/mnt/home-backup', how can you find the main volume mountpoint '/local' from that? Please explain how '/mnt/home-backup' is indeed "inherently rooted in the hierarchy of the volume itself", because there is always a "fixed relationship between the root directory inode of a subvolume and the root directory inode of any other subvolume or the main volume". [ ... ] > Again, it does, it's just not inherently exposed to userspace > unless you mount the top-level subvolume (subvolid=5 and/or > subvol=/ in mount options). This extra stupid point is based on ignoring that to "mount the top-level subvolume" relies on knowing already which one is the "top-level subvolume", which is begging the question. [ ... ] -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On Tue, 22 Aug 2017 17:45:37 +0200 Ulli Horlacherwrote: > In perl I have now: > > $root = $volume; > while (`btrfs subvolume show "$root" 2>/dev/null` !~ /toplevel subvolume/) { > $root = dirname($root); > last if $root eq '/'; > } > > If you are okay with rolling your own solutions like this, take a look at "btrfs filesystem usage ". It will print the blockdevice used for mounting the base FS. From that you can find the mountpoint via /proc/mounts. Performance-wise it seems to work instantly on an almost full 2TB FS. -- With respect, Roman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On Tue 2017-08-22 (11:03), Austin S. Hemmelgarn wrote: > Or alternatively, repeatedly call `btrfs filesystem show` on the path, > removing one component from the end each time until you get a zero > return code. The path you called it on that got a zero return code is > where the mount is (and thus what filesystem that subvolume is part of), > and the output just gave you a list of devices it's on. "btrfs filesystem show" is relative slow (2.6 s), "btrfs subvolume show" is MUCH faster (0.02 s). In perl I have now: $root = $volume; while (`btrfs subvolume show "$root" 2>/dev/null` !~ /toplevel subvolume/) { $root = dirname($root); last if $root eq '/'; } -- Ullrich Horlacher Server und Virtualisierung Rechenzentrum TIK Universitaet Stuttgart E-Mail: horlac...@tik.uni-stuttgart.de Allmandring 30aTel:++49-711-68565868 70569 Stuttgart (Germany) WWW:http://www.tik.uni-stuttgart.de/ REF:<62494c0c-0c27-5b36-3727-b8755eb2c...@gmail.com> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On 2017-08-22 10:43, Peter Grandi wrote: How do I find the root filesystem of a subvolume? Example: root@fex:~# df -T Filesystem Type 1K-blocks Used Available Use% Mounted on - -1073740800 104244552 967773976 10% /local/.backup/home [ ... ] I know, the root filesystem is /local, That question is somewhat misunderstood and uses the wrong concepts and terms. In UNIX filesystems a filesystem "root" is a directory inode with a number that is local to itself, and can be "mounted" anywhere, or left unmounted, and that is a property of the running system, not of the filesystem "root". Usually UNIX filesystems have a single "root" directory inode. In the case of Btrfs the main volume and its subvolumes all have filesystem "root" directory inodes, which may or may not be "mounted", anywhere the administrators of the running system pleases, as a property of the running system. There is no fixed relationship between the root directory inode of a subvolume and the root directory inode of any other subvolume or the main volume. Actually, there is, because it's inherently rooted in the hierarchy of the volume itself. That root inode for the subvolume is anchored somewhere under the next higher subvolume. It's the same concept as nested data-sets in ZFS, BTRFS just inherently exposes them at the appropriate location in the hierarchy and allows intermediary directories. Note: in Btrfs terminology "volume" seems to mean both the main volume and the collection of devices where it and subvolumes are hosted. Standard terminology from what I've seen uses 'volume' in the same way it's used for ext4, XFS, LVM, MD, and similar things, namely a BTRFS 'volume' is the collection of devices as well as the sum total of all subvolumes on those devices. This ends up meaning that it implicitly refers to the top-level subvolume when there are no other subvolumes, and as a result it's come to sometimes mean the top-level subvolume (though I rarely see that usage, and would actively discourage it). but who can I show it by command? The system does not keep an explicit record of which Btrfs "root" directory inode is related to which other Btrfs "root" directory inode in the same volume, whether mounted or unmounted. Again, it does, it's just not inherently exposed to userspace unless you mount the top-level subvolume (subvolid=5 and/or subvol=/ in mount options). Mount the top level subvolume (once you know what volume the subvolume is on), and call `btrfs subvolume list` on it. The `top level N` part of the output from that tells you what the next subvolume up the hierarchy is for each subvolume, and the `path` part at the end tells you the location within that next higher subvolume where this one is rooted. The output may not make sense though if you don't have the root subvolume mounted (because it may be non trivial to trace things up the tree). That relationship has to be discovered by using volume UUIDs, which are the same for the main subvolume and the other subvolumes, whether mounted or not, so one has to do: * For the indicated mounted subvolume "root" read its UUID. * For every mounted filesystem "root", check whether its type is 'btrfs' and if it is obtain its UUID. * If the UUID is the same, and the subvolume id is '5', that's the main subvolume, and terminate. * For every block device which is not mounted, check whether it has a Btrfs superblock. * If the type is 'btrfs' and the volume UUIS is the same as that of the subvolume, list the block device. In the latter case since the main volume is not mounted the only way to identify it is to list the block devices that host it. Or alternatively, repeatedly call `btrfs filesystem show` on the path, removing one component from the end each time until you get a zero return code. The path you called it on that got a zero return code is where the mount is (and thus what filesystem that subvolume is part of), and the output just gave you a list of devices it's on. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
> How do I find the root filesystem of a subvolume? > Example: > root@fex:~# df -T > Filesystem Type 1K-blocks Used Available Use% Mounted on > - -1073740800 104244552 967773976 10% /local/.backup/home [ ... ] > I know, the root filesystem is /local, That question is somewhat misunderstood and uses the wrong concepts and terms. In UNIX filesystems a filesystem "root" is a directory inode with a number that is local to itself, and can be "mounted" anywhere, or left unmounted, and that is a property of the running system, not of the filesystem "root". Usually UNIX filesystems have a single "root" directory inode. In the case of Btrfs the main volume and its subvolumes all have filesystem "root" directory inodes, which may or may not be "mounted", anywhere the administrators of the running system pleases, as a property of the running system. There is no fixed relationship between the root directory inode of a subvolume and the root directory inode of any other subvolume or the main volume. Note: in Btrfs terminology "volume" seems to mean both the main volume and the collection of devices where it and subvolumes are hosted. > but who can I show it by command? The system does not keep an explicit record of which Btrfs "root" directory inode is related to which other Btrfs "root" directory inode in the same volume, whether mounted or unmounted. That relationship has to be discovered by using volume UUIDs, which are the same for the main subvolume and the other subvolumes, whether mounted or not, so one has to do: * For the indicated mounted subvolume "root" read its UUID. * For every mounted filesystem "root", check whether its type is 'btrfs' and if it is obtain its UUID. * If the UUID is the same, and the subvolume id is '5', that's the main subvolume, and terminate. * For every block device which is not mounted, check whether it has a Btrfs superblock. * If the type is 'btrfs' and the volume UUIS is the same as that of the subvolume, list the block device. In the latter case since the main volume is not mounted the only way to identify it is to list the block devices that host it. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On 2017-08-22 10:23, Hugo Mills wrote: On Tue, Aug 22, 2017 at 10:12:25AM -0400, Austin S. Hemmelgarn wrote: On 2017-08-22 09:53, Ulli Horlacher wrote: On Tue 2017-08-22 (09:37), Austin S. Hemmelgarn wrote: root@fex:~# df -T /local/.backup/home Filesystem Type 1K-blocks Used Available Use% Mounted on - -1073740800 104252160 967766336 10% /local/.backup/home Hmm, now I'm really confused, I just checked on the Ubuntu 17.04 and 16.04.3 VM's I have (I only run current and the most recent LTS version), and neither of them behave like this. I have this kind of output on all of my Ubuntu hosts: root@moep:~# grep PRETTY_NAME /etc/os-release PRETTY_NAME="Ubuntu 16.04.3 LTS" root@moep:~# df -T /usb/UF/tmp/blubb Filesystem Type 1K-blocksUsed Available Use% Mounted on - - 12581888 3690524 7253700 34% /usb/UF/tmp/blubb root@moep:~# btrfs subvolume show /usb/UF/tmp/blubb /usb/UF/tmp/blubb Name: blubb UUID: ecf8c804-d4a3-9948-89fe-b0c1971c25cb Parent UUID:- Received UUID: - Creation time: 2017-08-22 12:54:16 +0200 Subvolume ID: 262 Generation: 23 Gen at creation:22 Parent ID: 5 Top level ID: 5 Flags: - Snapshot(s): root@moep:~# dpkg -l | grep btrfs ii btrfs-tools 4.4-1ubuntu1 amd64Checksumming Copy on Write Filesystem utilities Hmm, interesting. Are you using qgroups by chance? I get this behaviour (the "- -") only if it's a non-mounted subvolume: hrm@amelia:~ $ df -T . Filesystem Type 1K-blocks Used Available Use% Mounted on /dev/sdb1 btrfs 117220284 95271852 18611060 84% /home hrm@amelia:~ $ sudo btrfs sub crea foo Create subvolume './foo' hrm@amelia:~ $ df -T ./foo Filesystem Type 1K-blocks Used Available Use% Mounted on - -117220284 95271880 18611032 84% /home/hrm/foo hrm@amelia:~ $ sudo mkdir foo/bar hrm@amelia:~ $ df -T foo/bar Filesystem Type 1K-blocks Used Available Use% Mounted on - -117220284 95271852 18611060 84% /home/hrm/foo hrm@amelia:~ $ mkdir foo2 hrm@amelia:~ $ sudo mount /dev/sdb1 ./foo2 -o subvol=home/hrm/foo hrm@amelia:~ $ df -T foo2 Filesystem Type 1K-blocks Used Available Use% Mounted on /dev/sdb1 btrfs 117220284 95272384 18610528 84% /home/hrm/foo2 Wait, I think I see what's up here. I was just calling `df -T` without pointing at the subvolume (which correctly ignores it because it's not actually mounted). It looks like this is a side effect of the (rather irritating) fake mount-point behavior of subvolumes. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On Tue, Aug 22, 2017 at 10:12:25AM -0400, Austin S. Hemmelgarn wrote: > On 2017-08-22 09:53, Ulli Horlacher wrote: > >On Tue 2017-08-22 (09:37), Austin S. Hemmelgarn wrote: > > > >>>root@fex:~# df -T /local/.backup/home > >>>Filesystem Type 1K-blocks Used Available Use% Mounted on > >>>- -1073740800 104252160 967766336 10% /local/.backup/home > >> > >>Hmm, now I'm really confused, I just checked on the Ubuntu 17.04 and > >>16.04.3 VM's I have (I only run current and the most recent LTS > >>version), and neither of them behave like this. > > > >I have this kind of output on all of my Ubuntu hosts: > > > >root@moep:~# grep PRETTY_NAME /etc/os-release > >PRETTY_NAME="Ubuntu 16.04.3 LTS" > > > >root@moep:~# df -T /usb/UF/tmp/blubb > >Filesystem Type 1K-blocksUsed Available Use% Mounted on > >- - 12581888 3690524 7253700 34% /usb/UF/tmp/blubb > > > >root@moep:~# btrfs subvolume show /usb/UF/tmp/blubb > >/usb/UF/tmp/blubb > > Name: blubb > > UUID: ecf8c804-d4a3-9948-89fe-b0c1971c25cb > > Parent UUID:- > > Received UUID: - > > Creation time: 2017-08-22 12:54:16 +0200 > > Subvolume ID: 262 > > Generation: 23 > > Gen at creation:22 > > Parent ID: 5 > > Top level ID: 5 > > Flags: - > > Snapshot(s): > > > >root@moep:~# dpkg -l | grep btrfs > >ii btrfs-tools 4.4-1ubuntu1 > >amd64Checksumming Copy on Write Filesystem utilities > > > Hmm, interesting. Are you using qgroups by chance? I get this behaviour (the "- -") only if it's a non-mounted subvolume: hrm@amelia:~ $ df -T . Filesystem Type 1K-blocks Used Available Use% Mounted on /dev/sdb1 btrfs 117220284 95271852 18611060 84% /home hrm@amelia:~ $ sudo btrfs sub crea foo Create subvolume './foo' hrm@amelia:~ $ df -T ./foo Filesystem Type 1K-blocks Used Available Use% Mounted on - -117220284 95271880 18611032 84% /home/hrm/foo hrm@amelia:~ $ sudo mkdir foo/bar hrm@amelia:~ $ df -T foo/bar Filesystem Type 1K-blocks Used Available Use% Mounted on - -117220284 95271852 18611060 84% /home/hrm/foo hrm@amelia:~ $ mkdir foo2 hrm@amelia:~ $ sudo mount /dev/sdb1 ./foo2 -o subvol=home/hrm/foo hrm@amelia:~ $ df -T foo2 Filesystem Type 1K-blocks Used Available Use% Mounted on /dev/sdb1 btrfs 117220284 95272384 18610528 84% /home/hrm/foo2 Hugo. -- Hugo Mills | "Your problem is that you have a negative hugo@... carfax.org.uk | personality." http://carfax.org.uk/ | "No, I don't!" PGP: E2AB1DE4 | Londo and Vir, Babylon 5 signature.asc Description: Digital signature
Re: finding root filesystem of a subvolume?
On 2017-08-22 09:53, Ulli Horlacher wrote: On Tue 2017-08-22 (09:37), Austin S. Hemmelgarn wrote: root@fex:~# df -T /local/.backup/home Filesystem Type 1K-blocks Used Available Use% Mounted on - -1073740800 104252160 967766336 10% /local/.backup/home Hmm, now I'm really confused, I just checked on the Ubuntu 17.04 and 16.04.3 VM's I have (I only run current and the most recent LTS version), and neither of them behave like this. I have this kind of output on all of my Ubuntu hosts: root@moep:~# grep PRETTY_NAME /etc/os-release PRETTY_NAME="Ubuntu 16.04.3 LTS" root@moep:~# df -T /usb/UF/tmp/blubb Filesystem Type 1K-blocksUsed Available Use% Mounted on - - 12581888 3690524 7253700 34% /usb/UF/tmp/blubb root@moep:~# btrfs subvolume show /usb/UF/tmp/blubb /usb/UF/tmp/blubb Name: blubb UUID: ecf8c804-d4a3-9948-89fe-b0c1971c25cb Parent UUID:- Received UUID: - Creation time: 2017-08-22 12:54:16 +0200 Subvolume ID: 262 Generation: 23 Gen at creation:22 Parent ID: 5 Top level ID: 5 Flags: - Snapshot(s): root@moep:~# dpkg -l | grep btrfs ii btrfs-tools 4.4-1ubuntu1 amd64Checksumming Copy on Write Filesystem utilities Hmm, interesting. Are you using qgroups by chance? -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On Tue 2017-08-22 (09:37), Austin S. Hemmelgarn wrote: > > root@fex:~# df -T /local/.backup/home > > Filesystem Type 1K-blocks Used Available Use% Mounted on > > - -1073740800 104252160 967766336 10% /local/.backup/home > > Hmm, now I'm really confused, I just checked on the Ubuntu 17.04 and > 16.04.3 VM's I have (I only run current and the most recent LTS > version), and neither of them behave like this. I have this kind of output on all of my Ubuntu hosts: root@moep:~# grep PRETTY_NAME /etc/os-release PRETTY_NAME="Ubuntu 16.04.3 LTS" root@moep:~# df -T /usb/UF/tmp/blubb Filesystem Type 1K-blocksUsed Available Use% Mounted on - - 12581888 3690524 7253700 34% /usb/UF/tmp/blubb root@moep:~# btrfs subvolume show /usb/UF/tmp/blubb /usb/UF/tmp/blubb Name: blubb UUID: ecf8c804-d4a3-9948-89fe-b0c1971c25cb Parent UUID:- Received UUID: - Creation time: 2017-08-22 12:54:16 +0200 Subvolume ID: 262 Generation: 23 Gen at creation:22 Parent ID: 5 Top level ID: 5 Flags: - Snapshot(s): root@moep:~# dpkg -l | grep btrfs ii btrfs-tools 4.4-1ubuntu1 amd64Checksumming Copy on Write Filesystem utilities -- Ullrich Horlacher Server und Virtualisierung Rechenzentrum TIK Universitaet Stuttgart E-Mail: horlac...@tik.uni-stuttgart.de Allmandring 30aTel:++49-711-68565868 70569 Stuttgart (Germany) WWW:http://www.tik.uni-stuttgart.de/ REF:<0c35fba9-a514-31dd-a703-17f4727ed...@gmail.com> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
Hmm, now I'm really confused, I just checked on the Ubuntu 17.04 and 16.04.3 VM's I have (I only run current and the most recent LTS version), and neither of them behave like this. Was also shocked, but: $ lsb_release -a No LSB modules are available. Distributor ID:Ubuntu Description:Ubuntu 16.04.3 LTS Release:16.04 Codename:xenial $ df -T | grep /mnt/data/lxc $ df -T /mnt/data/lxc Filesystem Type 1K-blocks Used Available Use% Mounted on - -2907008836 90829848 2815107576 4% /mnt/data/lxc -- With Best Regards, Marat Khalili -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
I have no subvol=/ option at all: Probably depends on kernel, but I presume missing subvol means the same as subvol=/ . I am only interested in mounted volumes. If your initial path (/local/.backup/home) is a subvolume but it's not itself present in /proc/mounts then it's probably mounted as a part some higher-level subvolume, but this higher-level subvolume does not have to be root. Do you need volume root or just some higher-level subvolume that's mounted? -- With Best Regards, Marat Khalili -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On 2017-08-22 09:30, Ulli Horlacher wrote: On Tue 2017-08-22 (09:27), Austin S. Hemmelgarn wrote: root@fex:~# df -T Filesystem Type 1K-blocks Used Available Use% Mounted on - -1073740800 104244552 967773976 10% /local/.backup/home I've never seen the "- -" output from df before. Is this a bind mount or something? No, /local/.backup/home is just a btrfs subvolume It arguably shouldn't be showing up here then if it's not been explicitly mounted. I'm betting you're running OpenSUSE or SLES No: root@fex:~# cat /etc/os-release NAME="Ubuntu" VERSION="14.04.5 LTS, Trusty Tahr" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 14.04.5 LTS" VERSION_ID="14.04" HOME_URL="http://www.ubuntu.com/; SUPPORT_URL="http://help.ubuntu.com/; BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/; root@fex:~# df -T /local/.backup/home Filesystem Type 1K-blocks Used Available Use% Mounted on - -1073740800 104252160 967766336 10% /local/.backup/home root@fex:~# type df df is hashed (/bin/df) root@fex:~# dpkg -S /bin/df coreutils: /bin/df Hmm, now I'm really confused, I just checked on the Ubuntu 17.04 and 16.04.3 VM's I have (I only run current and the most recent LTS version), and neither of them behave like this. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On Tue 2017-08-22 (09:27), Austin S. Hemmelgarn wrote: > >>> root@fex:~# df -T > >>> Filesystem Type 1K-blocks Used Available Use% Mounted on > >>> - -1073740800 104244552 967773976 10% > >>> /local/.backup/home > >> > >> I've never seen the "- -" output from df before. Is this a bind > >> mount or something? > > > > No, /local/.backup/home is just a btrfs subvolume > > It arguably shouldn't be showing up here then if it's not been > explicitly mounted. I'm betting you're running OpenSUSE or SLES No: root@fex:~# cat /etc/os-release NAME="Ubuntu" VERSION="14.04.5 LTS, Trusty Tahr" ID=ubuntu ID_LIKE=debian PRETTY_NAME="Ubuntu 14.04.5 LTS" VERSION_ID="14.04" HOME_URL="http://www.ubuntu.com/; SUPPORT_URL="http://help.ubuntu.com/; BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/; root@fex:~# df -T /local/.backup/home Filesystem Type 1K-blocks Used Available Use% Mounted on - -1073740800 104252160 967766336 10% /local/.backup/home root@fex:~# type df df is hashed (/bin/df) root@fex:~# dpkg -S /bin/df coreutils: /bin/df -- Ullrich Horlacher Server und Virtualisierung Rechenzentrum TIK Universitaet Stuttgart E-Mail: horlac...@tik.uni-stuttgart.de Allmandring 30aTel:++49-711-68565868 70569 Stuttgart (Germany) WWW:http://www.tik.uni-stuttgart.de/ REF:<16778020-9167-b7cc-4768-ee33dca2b...@gmail.com> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On 2017-08-22 08:50, Ulli Horlacher wrote: On Tue 2017-08-22 (12:40), Hugo Mills wrote: On Tue, Aug 22, 2017 at 02:23:50PM +0200, Ulli Horlacher wrote: How do I find the root filesystem of a subvolume? Example: root@fex:~# df -T Filesystem Type 1K-blocks Used Available Use% Mounted on - -1073740800 104244552 967773976 10% /local/.backup/home I've never seen the "- -" output from df before. Is this a bind mount or something? No, /local/.backup/home is just a btrfs subvolume It arguably shouldn't be showing up here then if it's not been explicitly mounted. I'm betting you're running OpenSUSE or SLES and they finally got their df integration done, as that df output absolutely matches the type of brain-dead handling of BTRFS I'm coming to expect out of them. Note to SUSE people reading this: You should be including actual information for at least the Type field, and ideally the Filesystem field too. People expect this to behave reasonably, and not listing any info about where the 'mount' originated or what it is is not reasonable. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On Tue 2017-08-22 (15:58), Marat Khalili wrote: > On 22/08/17 15:50, Ulli Horlacher wrote: > > > It seems, I have to scan the subvolume path upwards until I found a real > > mount point, > > I think searching /proc/mounts for the same device and subvol=/ in > options is most straightforward. I have no subvol=/ option at all: root@fex:~# grep btrfs /proc/mounts /dev/sdf1 /backup btrfs rw,relatime,compress=zlib,space_cache 0 0 /dev/sde1 /local btrfs rw,relatime,compress=zlib,space_cache 0 0 > But what makes you think it's mounted at all? I am only interested in mounted volumes. -- Ullrich Horlacher Server und Virtualisierung Rechenzentrum TIK Universitaet Stuttgart E-Mail: horlac...@tik.uni-stuttgart.de Allmandring 30aTel:++49-711-68565868 70569 Stuttgart (Germany) WWW:http://www.tik.uni-stuttgart.de/ REF:-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On 22/08/17 15:50, Ulli Horlacher wrote: It seems, I have to scan the subvolume path upwards until I found a real mount point, I think searching /proc/mounts for the same device and subvol=/ in options is most straightforward. But what makes you think it's mounted at all? -- With Best Regards, Marat Khalili -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On Tue 2017-08-22 (12:40), Hugo Mills wrote: > On Tue, Aug 22, 2017 at 02:23:50PM +0200, Ulli Horlacher wrote: > > > How do I find the root filesystem of a subvolume? > > Example: > > > > root@fex:~# df -T > > Filesystem Type 1K-blocks Used Available Use% Mounted on > > - -1073740800 104244552 967773976 10% /local/.backup/home > >I've never seen the "- -" output from df before. Is this a bind > mount or something? No, /local/.backup/home is just a btrfs subvolume > > I know, the root filesystem is /local, but who can I show it by command? > >Probably in /proc/self/mountinfo root@fex:~# grep home /proc/self/mountinfo root@fex:~# grep btrfs /proc/self/mountinfo 31 22 0:23 / /backup rw,relatime - btrfs /dev/sdf1 rw,compress=zlib,space_cache 32 22 0:26 / /local rw,relatime - btrfs /dev/sde1 rw,compress=zlib,space_cache No information about the subvolume /local/.backup/home It seems, I have to scan the subvolume path upwards until I found a real mount point, -- Ullrich Horlacher Server und Virtualisierung Rechenzentrum TIK Universitaet Stuttgart E-Mail: horlac...@tik.uni-stuttgart.de Allmandring 30aTel:++49-711-68565868 70569 Stuttgart (Germany) WWW:http://www.tik.uni-stuttgart.de/ REF:<20170822124036.ga32...@carfax.org.uk> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: finding root filesystem of a subvolume?
On Tue, Aug 22, 2017 at 02:23:50PM +0200, Ulli Horlacher wrote: > How do I find the root filesystem of a subvolume? > Example: > > root@fex:~# df -T > Filesystem Type 1K-blocks Used Available Use% Mounted on > - -1073740800 104244552 967773976 10% /local/.backup/home I've never seen the "- -" output from df before. Is this a bind mount or something? > root@fex:~# btrfs subvolume show /local/.backup/home > /local/.backup/home > Name: home > uuid: f86a2db0-6a82-124f-9a71-1cd4c20fd6fb > Parent uuid:ba4d388f-44bf-7b46-b2b8-00e2a9a87181 > Creation time: 2017-08-10 22:19:15 > Object ID: 383 > Generation (Gen): 148 > Gen at creation:148 > Parent: 5 > Top Level: 5 > Flags: readonly > Snapshot(s): > > > I know, the root filesystem is /local, but who can I show it by command? Probably in /proc/self/mountinfo -- that should give you the full set of applied mount options, plus the original source for the mount (which will be a block device for most filesystem mounts, a path for bind mounts, or something FS-specific for network filesystems). Hugo. -- Hugo Mills | And what rough beast, its hour come round at last / hugo@... carfax.org.uk | slouches towards Bethlehem, to be born? http://carfax.org.uk/ | PGP: E2AB1DE4 | W.B. Yeats, The Second Coming signature.asc Description: Digital signature
finding root filesystem of a subvolume?
How do I find the root filesystem of a subvolume? Example: root@fex:~# df -T Filesystem Type 1K-blocks Used Available Use% Mounted on - -1073740800 104244552 967773976 10% /local/.backup/home root@fex:~# btrfs subvolume show /local/.backup/home /local/.backup/home Name: home uuid: f86a2db0-6a82-124f-9a71-1cd4c20fd6fb Parent uuid:ba4d388f-44bf-7b46-b2b8-00e2a9a87181 Creation time: 2017-08-10 22:19:15 Object ID: 383 Generation (Gen): 148 Gen at creation:148 Parent: 5 Top Level: 5 Flags: readonly Snapshot(s): I know, the root filesystem is /local, but who can I show it by command? -- Ullrich Horlacher Server und Virtualisierung Rechenzentrum TIK Universitaet Stuttgart E-Mail: horlac...@tik.uni-stuttgart.de Allmandring 30aTel:++49-711-68565868 70569 Stuttgart (Germany) WWW:http://www.tik.uni-stuttgart.de/ REF:<20170822122350.ga14...@rus.uni-stuttgart.de> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html