Re: [qubes-users] How Qubes / and /home/user mounting as different disks works?
so if I understood correctly, all the work is done inside the VM, not outside? I can imagine mounting the root disk as read only and then setting up my VM to 'write' to this disk using these pointers you mentioned. Is this how it work? Which solution Qubes uses and do you know one for Ubuntu? I don't want to have lots of different VMs, Ubuntu is enough On Thursday, March 5, 2020 at 1:56:39 AM UTC-3, Chris Laprise wrote: > > On 3/4/20 10:19 PM, Guerlan wrote: > > I'm curious about how Qubes does this: > > > > mounts /home/user and other user-related directories from disk B > > mounts the / from disk A, but when VM shutdowns, disk is discarded > > > > I'm curious on how it mounts disk A. I don't think it makes a copy of > > disk A to a temporary disk A', because that'd move lots of gigabytes on > > every VM startup. > > However, it also can't mount disk A as read-only, because I can write to > > it, it just gets discarded. > > How does this work? And is it exclusive of Xen? Couldn't I do the same > > in KVM? It's very useful > > As to whether this can be done with KVM, yes you can. But Linux vendors > are very confused about which copy-on-write technologies to promote so > they tend to push the least common denominator, which is partitions or > VMDK files. OTOH, Qubes decided copy-on-write storage was too useful to > ignore and integrated it into VM management functions. > > You could use LVM thin pools with KVM, but IIRC you would have to > automate snapshot handling yourself or find an additional package to do > it (if such exists). > > -- > Chris Laprise, tas...@posteo.net > https://github.com/tasket > https://twitter.com/ttaskett > PGP: BEE2 20C5 356E 764A 73EB 4AB3 1DC4 D106 F07F 1886 > -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/a67e7abc-4fda-4d87-bbca-a4c07b7835db%40googlegroups.com.
Re: [qubes-users] How Qubes / and /home/user mounting as different disks works?
On 3/4/20 10:19 PM, Guerlan wrote: I'm curious about how Qubes does this: mounts /home/user and other user-related directories from disk B mounts the / from disk A, but when VM shutdowns, disk is discarded I'm curious on how it mounts disk A. I don't think it makes a copy of disk A to a temporary disk A', because that'd move lots of gigabytes on every VM startup. However, it also can't mount disk A as read-only, because I can write to it, it just gets discarded. How does this work? And is it exclusive of Xen? Couldn't I do the same in KVM? It's very useful As to whether this can be done with KVM, yes you can. But Linux vendors are very confused about which copy-on-write technologies to promote so they tend to push the least common denominator, which is partitions or VMDK files. OTOH, Qubes decided copy-on-write storage was too useful to ignore and integrated it into VM management functions. You could use LVM thin pools with KVM, but IIRC you would have to automate snapshot handling yourself or find an additional package to do it (if such exists). -- Chris Laprise, tas...@posteo.net https://github.com/tasket https://twitter.com/ttaskett PGP: BEE2 20C5 356E 764A 73EB 4AB3 1DC4 D106 F07F 1886 -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/c207011a-9ad5-935c-f677-866c7aa0c831%40posteo.net.
Re: [qubes-users] How Qubes / and /home/user mounting as different disks works?
On 3/4/20 10:19 PM, Guerlan wrote: I'm curious about how Qubes does this: mounts /home/user and other user-related directories from disk B mounts the / from disk A, but when VM shutdowns, disk is discarded I'm curious on how it mounts disk A. I don't think it makes a copy of disk A to a temporary disk A', because that'd move lots of gigabytes on every VM startup. However, it also can't mount disk A as read-only, because I can write to it, it just gets discarded. How does this work? And is it exclusive of Xen? Couldn't I do the same in KVM? It's very useful Qubes uses copy-on-write snapshots to achieve this. With a default install, that means an LVM "thin pool" holds all of the VM volumes, and when a VM starts a snapshot is taken of both "disk A" and "disk B" (the *-root and *-private volumes). With a normal AppVM (base on a template) the root and private volumes are treated differently on shutdown: Root snapshot is discarded, and private is rotated to replace the persistent copy (what appears in the VM as /rw and /home). A similar snapshot routine is used if you installed Qubes with Btrfs format instead of LVM (Btrfs is a copy-on-write filesystem). Copy-on-write provides the ability to create new representations or snapshots of an existing file or volume, instantly. Snapshotting is like copying, but using a collection of pointers instead of the data itself. Thus, when a new snapshot is changed, the system only needs to write some new blocks in a different location and replace some pointers in the snapshot's metadata to point to the new location. This all can save a lot of time and disk space. -- Chris Laprise, tas...@posteo.net https://github.com/tasket https://twitter.com/ttaskett PGP: BEE2 20C5 356E 764A 73EB 4AB3 1DC4 D106 F07F 1886 -- You received this message because you are subscribed to the Google Groups "qubes-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/qubes-users/809ee2c9-e860-92cc-4f68-8d965c9eda26%40posteo.net.
