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| layout | title | permalink | redirect_from | |
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| doc | Managing VM kernel | /doc/managing-vm-kernel/ |
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VM kernel managed by dom0
By default VMs kernels are provided by dom0. This means that:
- You can select kernel version in VM settings;
- You can modify kernel options in VM settings;
- You can not modify any of above from inside of VM;
- Installing additional kernel modules is cumbersome.
To select which kernel a given VM will use, you can use either use Qubes Manager (VM settings, advanced tab), or qvm-prefs tool:
[user@dom0 ~]$ qvm-prefs my-appvm -s kernel
Missing kernel version argument!
Possible values:
1) default
2) none (kernels subdir in VM)
3) <kernel version>, one of:
- 3.18.16-3
- 3.18.17-4
- 3.19.fc20
- 3.18.10-2
[user@dom0 ~]$ qvm-prefs my-appvm -s kernel 3.18.17-4
[user@dom0 ~]$ qvm-prefs my-appvm -s kernel default
To check/change the default kernel you can go either to "Global settings" in Qubes Manager, or use qubes-prefs tool:
[user@dom0 ~]$ qubes-prefs
clockvm : sys-net
default-fw-netvm : sys-net
default-kernel : 3.18.17-4
default-netvm : sys-firewall
default-template : fedora-21
updatevm : sys-firewall
[user@dom0 ~]$ qubes-prefs -s default-kernel 3.19.fc20
Installing different kernel using Qubes kernel package
VM kernels are packages by Qubes team in kernel-qubes-vm packages. Generally system will keep the 3 newest available versions. You can list them with the rpm command:
[user@dom0 ~]$ rpm -qa 'kernel-qubes-vm*'
kernel-qubes-vm-3.18.10-2.pvops.qubes.x86_64
kernel-qubes-vm-3.18.16-3.pvops.qubes.x86_64
kernel-qubes-vm-3.18.17-4.pvops.qubes.x86_64
If you want more recent version, you can check qubes-dom0-unstable repository. As the name suggest, keep in
mind that those packages may be less stable than the default ones.
Checking available versions in qubes-dom0-unstable repository:
[user@dom0 ~]$ sudo qubes-dom0-update --enablerepo=qubes-dom0-unstable --action=list kernel-qubes-vm
Using sys-firewall as UpdateVM to download updates for Dom0; this may take some time...
Running command on VM: 'sys-firewall'...
Loaded plugins: langpacks, post-transaction-actions, yum-qubes-hooks
Installed Packages
kernel-qubes-vm.x86_64 1000:3.18.10-2.pvops.qubes installed
kernel-qubes-vm.x86_64 1000:3.18.16-3.pvops.qubes installed
kernel-qubes-vm.x86_64 1000:3.18.17-4.pvops.qubes installed
Available Packages
kernel-qubes-vm.x86_64 1000:4.1.12-6.pvops.qubes qubes-dom0-unstable
No packages downloaded
Installed Packages
kernel-qubes-vm.x86_64 1000:3.18.10-2.pvops.qubes @anaconda/R3.0
kernel-qubes-vm.x86_64 1000:3.18.16-3.pvops.qubes @/kernel-qubes-vm-3.18.16-3.pvops.qubes.x86_64
kernel-qubes-vm.x86_64 1000:3.18.17-4.pvops.qubes @qubes-dom0-cached
Installing new version from qubes-dom0-unstable repository:
[user@dom0 ~]$ sudo qubes-dom0-update --enablerepo=qubes-dom0-unstable kernel-qubes-vm
Using sys-firewall as UpdateVM to download updates for Dom0; this may take some time...
Running command on VM: 'sys-firewall'...
Loaded plugins: langpacks, post-transaction-actions, yum-qubes-hooks
Resolving Dependencies
(...)
===========================================================================================
Package Arch Version Repository Size
===========================================================================================
Installing:
kernel-qubes-vm x86_64 1000:4.1.12-6.pvops.qubes qubes-dom0-cached 40 M
Removing:
kernel-qubes-vm x86_64 1000:3.18.10-2.pvops.qubes @anaconda/R3.0 134 M
Transaction Summary
===========================================================================================
Install 1 Package
Remove 1 Package
Total download size: 40 M
Is this ok [y/d/N]: y
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction (shutdown inhibited)
Installing : 1000:kernel-qubes-vm-4.1.12-6.pvops.qubes.x86_64 1/2
mke2fs 1.42.12 (29-Aug-2014)
This kernel version is used by at least one VM, cannot remove
error: %preun(kernel-qubes-vm-1000:3.18.10-2.pvops.qubes.x86_64) scriptlet failed, exit status 1
Error in PREUN scriptlet in rpm package 1000:kernel-qubes-vm-3.18.10-2.pvops.qubes.x86_64
Verifying : 1000:kernel-qubes-vm-4.1.12-6.pvops.qubes.x86_64 1/2
Verifying : 1000:kernel-qubes-vm-3.18.10-2.pvops.qubes.x86_64 2/2
Installed:
kernel-qubes-vm.x86_64 1000:4.1.12-6.pvops.qubes
Failed:
kernel-qubes-vm.x86_64 1000:3.18.10-2.pvops.qubes
Complete!
[marmarek@dom0 ~]$
In the above example, it tries to remove 3.18.10-2.pvops.qubes kernel (to keep only 3 installed), but since some VM uses it, it fails. Installation of new package is unaffected by this event.
The newly installed package is set as default VM kernel.
Installing different VM kernel based on dom0 kernel
It is possible to package kernel installed in dom0 as VM kernel. This makes it possible to use VM kernel, which is not packaged by Qubes team. This includes:
- using Fedora kernel package
- using manually compiled kernel
To prepare such VM kernel, you need to install qubes-kernel-vm-support
package in dom0 and also have matching kernel headers installed (kernel-devel
package in case of Fedora kernel package). You can install required stuff using qubes-dom0-update:
[user@dom0 ~]$ sudo qubes-dom0-update qubes-kernel-vm-support kernel-devel
Using sys-firewall as UpdateVM to download updates for Dom0; this may take some time...
Running command on VM: 'sys-firewall'...
Loaded plugins: langpacks, post-transaction-actions, yum-qubes-hooks
Package 1000:kernel-devel-4.1.9-6.pvops.qubes.x86_64 already installed and latest version
Resolving Dependencies
(...)
================================================================================
Package Arch Version Repository Size
================================================================================
Installing:
qubes-kernel-vm-support x86_64 3.1.2-1.fc20 qubes-dom0-cached 9.2 k
Transaction Summary
================================================================================
Install 1 Package
Total download size: 9.2 k
Installed size: 13 k
Is this ok [y/d/N]: y
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction (shutdown inhibited)
Installing : qubes-kernel-vm-support-3.1.2-1.fc20.x86_64 1/1
Creating symlink /var/lib/dkms/u2mfn/3.1.2/source ->
/usr/src/u2mfn-3.1.2
DKMS: add completed.
Verifying : qubes-kernel-vm-support-3.1.2-1.fc20.x86_64 1/1
Installed:
qubes-kernel-vm-support.x86_64 0:3.1.2-1.fc20
Complete!
Then you can call qubes-prepare-vm-kernel tool to actually package the
kernel. The first parameter is kernel version (exactly as seen by the kernel),
the second one (optional) is short name being visible in Qubes Manager and
qvm-prefs tool.
[user@dom0 ~]$ sudo qubes-prepare-vm-kernel 4.1.9-6.pvops.qubes.x86_64 4.1.qubes
--> Building files for 4.1.9-6.pvops.qubes.x86_64 in /var/lib/qubes/vm-kernels/4.1.qubes
---> Recompiling kernel module (u2mfn)
---> Generating modules.img
mke2fs 1.42.12 (29-Aug-2014)
---> Generating initramfs
--> Done.
Using kernel installed in the VM
This option is available only in Qubes R3.1 or newer
It is possible to use kernel installed in the VM (in most cases - TemplateVM). This is possible thanks to PV GRUB2 - GRUB2 running in the VM. To make it happen, you need to:
- Install PV GRUB2 in dom0 - package is named
grub2-xen. - Install kernel in the VM. As with all VM software installation - this needs to be done in TemplateVM (of StandaloneVM if you are using one).
- Set VM kernel to
pvgrub2value. You can usepvgrub2in selected VMs, not necessary all of them, even when it's template has kernel installed. You can still use dom0-provided kernel for selected VMs.
WARNING: When using kernel from within VM, kernelopts parameter is ignored.
Installing PV GRUB2
Simply execute:
sudo qubes-dom0-update grub2-xen
Installing kernel in Fedora VM
In Fedora based VM, you need to install qubes-kernel-vm-support package. This
package include required additional kernel module and initramfs addition
required to start Qubes VM (for details see
template implementation). Additionally you
need some GRUB tools to create it's configuration. Note: you don't need actual
grub bootloader as it is provided by dom0. But having one also shouldn't harm.
sudo yum install qubes-kernel-vm-support grub2-tools
Then install whatever kernel you want. If you are using distribution kernel
package (kernel package), initramfs and kernel module should be handled
automatically, but you need to ensure you have kernel-devel package for the
same kernel version installed. If you are using manually build kernel, you need
to handle this on your own. Take a look at dkms and dracut documentation.
Especially dkms autoinstall command may be useful.
When kernel is installed, you need to create GRUB configuration.
You may want to adjust some settings in /etc/default/grub, for example lower
GRUB_TIMEOUT to speed up VM startup. Then you need to generate actual configuration:
In Fedora it can be done using grub2-mkconfig tool:
sudo grub2-mkconfig -o /boot/grub2/grub.cfg
You can safely ignore this error message:
grub2-probe: error: cannot find a GRUB drive for /dev/mapper/dmroot. Check your device.map
Then shutdown the VM. From now you can set pvgrub2 as VM kernel and it will
start kernel configured within VM.
Installing kernel in Debian VM
In Debian based VM, you need to install qubes-kernel-vm-support package. This
package include required additional kernel module and initramfs addition
required to start Qubes VM (for details see
template implementation). Additionally you
need some GRUB tools to create it's configuration. Note: you don't need actual
grub bootloader as it is provided by dom0. But having one also shouldn't harm.
sudo apt-get update
sudo apt-get install qubes-kernel-vm-support grub2-common
Ignore warnings about version '...' has bad syntax.
Then install whatever kernel you want. If you are using distribution kernel
package (linux-image-amd64 package), initramfs and kernel module should be
handled automatically. If not, or you are building kernel manually, do this on
using dkms and initramfs-tools:
sudo dkms autoinstall -k <kernel-version> # replace this <kernel-version> with actual kernel version
sudo update-initramfs -u
The output should look like this:
$ sudo dkms autoinstall -k 3.16.0-4-amd64
u2mfn:
Running module version sanity check.
- Original module
- No original module exists within this kernel
- Installation
- Installing to /lib/modules/3.16.0-4-amd64/updates/dkms/
depmod....
DKMS: install completed.
$ sudo update-initramfs -u
update-initramfs: Generating /boot/initrd.img-3.16.0-4-amd64
When kernel is installed, you need to create GRUB configuration.
You may want to adjust some settings in /etc/default/grub, for example lower
GRUB_TIMEOUT to speed up VM startup. Then you need to generate actual configuration:
In Fedora it can be done using update-grub2 tool:
sudo mkdir /boot/grub
sudo update-grub2
You can safely ignore this error message:
grub2-probe: error: cannot find a GRUB drive for /dev/mapper/dmroot. Check your device.map
Then shutdown the VM. From now you can set pvgrub2 as VM kernel and it will
start kernel configured within VM.
When starting the VM you can safely ignore any warnings about a missing module 'dummy-hcd'
Troubleshooting
In case of problems, you can access VM console (using sudo xl console VMNAME in dom0) to access
GRUB menu. You need to call it just after starting VM (until GRUB_TIMEOUT
expires) - for example in separate dom0 terminal window.
In any case you can later access VM logs (especially VM console log (guest-VMNAME.log).
You can always set kernel back to some dom0-provided value to fix VM kernel installation.