From 543413c1598778104a94aaeb1a8d0f882f2eb927 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Marek=20Marczykowski-G=C3=B3recki?= Date: Thu, 15 Sep 2011 19:40:20 +0000 Subject: [PATCH] TemplateImplementation changed --- TemplateImplementation.md | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/TemplateImplementation.md b/TemplateImplementation.md index 0c4f51a1..4257837a 100644 --- a/TemplateImplementation.md +++ b/TemplateImplementation.md @@ -4,6 +4,38 @@ title: TemplateImplementation permalink: /wiki/TemplateImplementation/ --- +Overview of VM block devices +============================ + +Every VM has 4 block devices connected: + +- **xvda** - base root device (/) - details described below +- **xvdb** - private.img - place where VM always can write. +- **xvdc** - volatile.img, discarded at each VM restart - here is placed swap and temporal "/" modifications (see below) +- **xvdd** - modules.img - kernel modules and firmware + +private.img (xvdb) +------------------ + +This is mounted as /rw and here is placed all VM private data. This includes: + +- */home* - which is symlink to /rw/home +- */usr/local* - which is symlink to /rw/usrlocal +- some config files (/rw/config) called by qubes core scripts (ex /rw/config/rc.local) + +modules.img (xvdd) +------------------ + +As kernel is chosen in dom0, not VM there must be some way to provide matching kernel modules to VM OS. Qubes kernel dir consists of 3 files: + +- *vmlinuz* - actual kernel +- *initramfs* - initial ramdisk containing script to setup snapshot devices (see below) and mount /lib/modules +- *modules.img* - filesystem image of /lib/modules with matching kernel modules and firmware (/lib/firmware/updates is symlinked to /lib/modules/firmware) + +Normally kernel "package" is common for many VMs (can be set using qvm-prefs). One of them can be set as default (qvm-set-default-kernel) to simplify kernel updates (by default all VMs uses default kernel). All installed kernels are placed in /var/lib/qubes/vm-kernels as separate subdirs. In this case, modules.img is attached to VM as R/O device. + +There is special case when VM can have custom kernel - when it is updateable (StandaloneVM or TemplateVM) and kernel is set to "none" (by qvm-prefs). In this case VM uses kernel from "kernels" VM subdir and modules.img is attached as R/W device. FIXME: "none" should be renamed to "custom". + Qubes TemplateVM implementation ===============================