Create Alpine Linux PV DomU: Difference between revisions

Revision as of 14:53, 18 August 2023

Obtain a copy of Alpine Linux

To create an Alpine Linux paravirtualized (PV) DomU you'll need an Alpine Linux iso.

Download the latest alpine-virt iso from https://alpinelinux.org/downloads/

In this example we'll use /data/ for the download and disk images.

Mount the ISO image

Next, mount the iso so you can read the kernel and initramfs:

mount -t iso9660 -o loop /data/alpine-virt-3.20.3-x86_64.iso /media/cdrom

Now you have the kernel in /media/cdrom/boot/vmlinuz-virt and initramfs in /media/cdrom/boot/initramfs-virt.

Alternatively you can use uniso or p7zip to extract the content to a temporary area.

Create the disk image

Now you need to create an empty file to be used as the hard drive of the DomU (in this example we are using a 3GB disk):

dd if=/dev/zero of=/data/a1.img bs=1M count=3000

Alternatively, if an LVM volume group (e.g. vg1) with free space is available on dom0, create a logical volume for Alpine:

sudo lvcreate -n alpine -L 10g vg1

Create a DomU config file that boots the ISO image

Next, create a basic DomU configuration file, so you can launch the pv guest iso (save it where you like, although the most common place is /etc/xen/).

Contents of /etc/xen/a1.cfg

 # Alpine Linux PV DomU

# Kernel paths for install
kernel = "/media/cdrom/boot/vmlinuz-virt"
ramdisk = "/media/cdrom/boot/initramfs-virt"
extra="modules=loop,squashfs console=hvc0"

# Path to HDD and iso file
disk = [
        'format=raw, vdev=xvda, access=w, target=/data/a1.img',
        'format=raw, vdev=xvdc, access=r, devtype=cdrom, target=/data/alpine-virt-3.20.3-x86_64.iso'
       ]

# Network configuration
vif = ['bridge=br0']

# DomU settings
memory = 512
name = "alpine-a1"
vcpus = 1
maxvcpus = 1

If using LVM, replace /data/a1.img with /dev/vg1/alpine in the disk specification.

Install the guest

Now that you have the necessary files, you can start the DomU to proceed with the install:

xl create -f /etc/xen/a1.cfg -c

Log into the system with user "root" and no password.

After configuring the basic system, you will be asked where would you like to install Alpine. Choose xvda and sys.

That will create three partitions on your disk. xvda1 for /boot, xvda2 for swap and xvda3 for /

Available disks are:
  xvda	(3.1 GB  )
Which disk(s) would you like to use? (or '?' for help or 'none') [none] xvda
The following disk is selected:
  xvda	(3.1 GB  )
How would you like to use it? ('sys', 'data' or '?' for help) [?] sys
WARNING: The following disk(s) will be erased:
  xvda	(3.1 GB  )
WARNING: Erase the above disk(s) and continue? [y/N]: y
Initializing partitions on /dev/xvda...
Creating file systems...
Installing system on /dev/xvda3:


Installation is complete. Please reboot.

#

When you reboot, the pv bootloader pvgrub, will look to /boot/grub/grub.cfg for its menu, so create that file first.

Mount the boot partition and create a grub/grub.cfg file for pvgrub. (Note that grub.cfg is for pvgrub2 which replaced pvgrub1 and its menu.lst beginning in 2013.)

mount /dev/xvda1 /mnt mkdir /mnt/grub

Install a basic text editor like nano or vim:

apk add nano

If using nano, enter:

nano /mnt/grub/grub.cfg

Then add the following to create a basic grub2 configuration file:

Contents of /mnt/grub/grub.cfg

menuentry 'alpine-xen' {
    set root=(xen/xvda,msdos1)
    linux /boot/vmlinuz-virt root=/dev/xvda3 modules=ext4 console=hvc0
    initrd /boot/initramfs 
 }

Finally, Ctrl-S to save, Ctrl-X to exit nano.

Unmount and power off.

umount /mnt poweroff

Adjust the domU config file to boot from fresh install

In your Dom0, edit your DomU config file to boot with pvgrub.

Contents of /etc/xen/a1.cfg

# Alpine Linux PV DomU

kernel = "/usr/lib/xen/boot/pv-grub-x86_64.gz"

# Path to HDD and iso file
disk = [
        'format=raw, vdev=xvda, access=w, target=/data/a1.img'
       ]

# Network configuration
vif = ['bridge=br0']

# DomU settings
memory = 512
name = "alpine-a1"
vcpus = 1
maxvcpus = 1

The name and location of pvgrub in Dom0 is distribution-specific, so you may need to change the "kernel=" line, above.

For example, in Debian 10, it's '/usr/lib/grub-xen/grub-x86_64-xen.bin'

Remember to unmount the loopback iso image.

umount /media/cdrom

The next time you boot, you'll be presented with the grub boot menu, and your VM will boot.