-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 On Mon, Jul 14, 2025 at 10:26:00AM +0000, qubes...@4forl1st5.slmail.me wrote: > On Sunday, July 13th, 2025 at 11:10, Marek Marczykowski-Górecki > <marma...@invisiblethingslab.com> wrote: > > > > The above documentation is outdated a bit - ... > > Ah-ha: thanks for pointing that out. > > > > ... with LVM thin provisioning > > the CoW layer on root volume is done in dom0, so VM gets read-write > > snapshot as xvda and doesn't need to do CoW on its own. > > Yeah: so I did dump, and take a look in, the virsh files and saw the > read-write config there, but clearly didn't appreciate the implications > of it, especially as I was looking for something read-only. > > I just assumed I had missed something. > > > > So, volatile > volume is used only for swap. > > To just clarify that last bit though: > > the 9G partition in the volatile VBD doesn't even play a part in the > in-Dom0 CoW layering: it's just 9G of unused space in a 10G volume > that will get created for every VM instance?
Yes, when the CoW layer is done in dom0, that 9G partition is unused. Thanks to thin provisioning/sparse files it doesn't occupy disk space either, so it's harmless. Some users use this it for a larger temp directory or more swap. In fact, it's specifically created as xvdc3 (instead of xvdc2) when it's unused, to ease detection when it's safe to use it. > Asking, as I have an old laptop on which I haven't been able to get > Qubes to install, but was hoping to still replicate most of the Qubes > compartmentalisation for the VMs, but running a vanilla Xen. > > > > > Generally VM's initramfs takes care of assembling /dev/mapper/dmroot. > > But if you look closely, /dev/mapper/dmroot is simply a symlink to > > /dev/xvda3. > > That may well have been a case of not seeing the wood for the trees, > because I thought I was in the middle of a dmsetup forest! Yeah, it is confusing a bit. In fact, earlier even in this case there was device-mapper involved, just dm-linear to map it 1:1 to xvda3. But later we simplified it to a symlink (one layer less) but keeping the name so it's always /dev/mapper/dmroot regardless of the configuration (so configs like /etc/fstab stays the same). - -- Best Regards, Marek Marczykowski-Górecki Invisible Things Lab -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhrpukzGPukRmQqkK24/THMrX1ywFAmh03WgACgkQ24/THMrX 1yxWiQf/cnms5RoRZHnb18ZwHC2lR8uA4RmioHIH68KWzuUWHvqNfqlJzPl1bEGR qfJO9zxuGk3seRasLMSh/725sZkRf4mW0/+FBx/ZgvGSBLYVRhAsWxzK2+1MTQWt p4uq5WRhL159BfxJZSQAvNZjo+uVRwcZzvry0VmBwYD9cT1BZURdOce/Epg7HHA+ 71K34xFBtP1CXEx4SKv65Uis+A64RUpRMGBiJcqSz3Tc7ULKqGQbBSCdT6LBBAUV dCNPqIDy+7SVaAPa1Hq/K5ZHRfzA9n22HBy5J2EUHu3FstNIbsRbjBOj0u7pjMbE SET8l3RE8YtJTQvEbtwV8J4Y2bPJZw== =oz7c -----END PGP SIGNATURE----- -- You received this message because you are subscribed to the Google Groups "qubes-devel" group. To unsubscribe from this group and stop receiving emails from it, send an email to qubes-devel+unsubscr...@googlegroups.com. To view this discussion visit https://groups.google.com/d/msgid/qubes-devel/aHTdaHAjOGc_zQRE%40mail-itl.
