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R3.2 updates

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spell out dracut step in fedora template
add version notes
add note about first boot delay
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configuration/managing-vm-kernel.md
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@ -16,10 +16,13 @@ By default, VMs kernels are provided by dom0. This means that:
3. You can **not** modify any of the above from inside a VM;
4. Installing additional kernel modules is cumbersome.
*Note* In the examples below, although the specific version numbers might be old, the commands have been verified on R3.2 with debian-9 and fedora-26 templates.
At the time of writing, there is a blocking issue for R4.0 [3563](https://github.com/QubesOS/qubes-issues/issues/3563).
To select which kernel a given VM will use, you can either use Qubes Manager (VM settings, advanced tab), or the `qvm-prefs` tool:
~~~
[user@dom0 ~]$ qvm-prefs my-appvm -s kernel
[user@dom0 ~]$ qvm-prefs -s my-appvm kernel
Missing kernel version argument!
Possible values:
1) default
@ -29,8 +32,8 @@ Possible values:
- 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
[user@dom0 ~]$ qvm-prefs -s my-appvm kernel 3.18.17-4
[user@dom0 ~]$ qvm-prefs -s my-appvm kernel default
~~~
To check/change the default kernel you can either go to "Global settings" in Qubes Manager, or use the `qubes-prefs` tool:
@ -211,13 +214,13 @@ Using kernel installed in the VM
It is possible to use a 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:
To make it happen, at a high level you need to:
1. Install PV GRUB2 in dom0 - package is named `grub2-xen`.
2. 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).
1. Install PV GRUB2 (`grub2-xen`) in dom0.
2. Install kernel in the VM (see below for Fedora and Debian steps).
As with all VM software installation - this needs to be done in a TemplateVM (or StandaloneVM if you are using one).
3. Set VM kernel to `pvgrub2` value.
You can use `pvgrub2` in selected VMs, but it's not necessary in all of them, even when its template has a kernel installed.
You can use `pvgrub2` in selected VMs, but it's not necessary in all of them, even if its template has a kernel installed.
You can still use a dom0-provided kernel for selected VMs.
**WARNING: When using a kernel from within a VM, the `kernelopts` parameter is ignored.**
@ -238,15 +241,22 @@ Additionally, you need some GRUB tools to create its configuration.
Note: You don't need an actual grub bootloader as it is provided by dom0, but having one shouldn't hurt.
~~~
sudo yum install qubes-kernel-vm-support grub2-tools
sudo dnf install qubes-kernel-vm-support grub2-tools
~~~
Then install whatever kernel you want.
If you are using distribution kernel package (`kernel` package), the initramfs and kernel module should be handled automatically, but you need to ensure you have the `kernel-devel` package for the same kernel version installed.
If you are using a manually built kernel, you need to handle this on your own.
Take a look at the `dkms` and `dracut` documentation, especially the `dkms autoinstall` command may be useful.
You need to also ensure you have the `kernel-devel` package for the same kernel version installed.
When the kernel is installed, you need to create a GRUB configuration.
If you are using a distribution kernel package (`kernel` package), the initramfs and kernel modules may be handled automatically.
If you are using a manually built kernel, you need to handle this on your own.
Take a look at the `dkms` documentation, especially the `dkms autoinstall` command may be useful.
If you did not see the `kernel` install rebuild your initramfs, or are using a manually built kernel, you will need to rebuild it yourself with the following (replace version numbers with those appropriate for your kernel):
~~~
dracut -f /boot/initramfs-4.14.16-200.fc26.x86_64.img 4.14.16-200.fc26.x86_64
~~~
Once the kernel is installed, you need to create a 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 the actual configuration:
In Fedora it can be done using the `grub2-mkconfig` tool:
@ -264,6 +274,11 @@ grub2-probe: error: cannot find a GRUB drive for /dev/mapper/dmroot. Check your
Then shutdown the VM.
Now you can set `pvgrub2` as the VM kernel and it will start the kernel configured within your VM.
**Note:** On first boot the VM will automatically allocate swap space.
This can take a while to complete- longer than your `qrexec_timeout` setting, which will make the VM appear to have hung on boot.
To confirm this is the case, see [Troubleshooting](/doc/managing-vm-kernel/#troubleshooting) below or just wait for five minutes and shutdown the VM.
It should respond normally on future boots.
### Installing kernel in Debian VM
In a Debian based VM, you need to install the `qubes-kernel-vm-support` package.
@ -272,10 +287,13 @@ Additionally, you need some GRUB tools to create its configuration.
Note: You don't need an actual grub bootloader as it is provided by dom0, but having one shouldn't hurt.
~~~
sudo apt-get update
sudo apt-get install qubes-kernel-vm-support grub2-common
sudo apt update
sudo apt install qubes-kernel-vm-support grub2-common
~~~
If prompted for a GRUB install device, choose `/dev/mapper/dmroot`.
You will receive an error about GRUB failed to install to it, but just continue anyways.
You don't need an actual grub bootloader as it is provided by dom0, but having one shouldn't hurt.
Ignore warnings about `version '...' has bad syntax`.
Then install whatever kernel you want.
@ -322,6 +340,11 @@ Now you can set `pvgrub2` as the VM kernel and it will start the kernel configur
When starting the VM you can safely ignore any warnings about a missing module 'dummy-hcd'.
**Note:** on first boot the VM will automatically allocate swap space.
This can take a while to complete- longer than your `qrexec_timeout` setting, which will make the VM appear to have hung on boot.
To confirm this is the case, see [Troubleshooting](/doc/managing-vm-kernel/#troubleshooting) below or just wait for five minutes and shutdown the VM.
It should respond normally on future boots.
### Troubleshooting
In case of problems, you can access the VM console using `sudo xl console VMNAME` in dom0, then access the GRUB menu.