- preseed
- Jonathan Haack
- Haack's Networking
- webmaster@haacksnetworking.org
preseed
I created my own virtualization stack about two and a half years ago. As I expanded and needed to spin up VMs, my first strategy was to create model VMs that fit particular use cases and then virt-clone those and then adapt to the new use case. Over time, this became cumbersome, and I started having use-cases that did not fit the templates. For this reason, it came to time to automate fresh Debian installs on new VMs. After studying forums, I saw that Debian had an “auto-installer” feature and that you could pass configs to it through virsh by adding a few xml lines. After a little trial and error with using a remote site for the config vs. localhost, I learned that you could pass the preseed config file to virsh with the last line in this block:
virt-install --name=domain.org.qcow2 \ --os-variant=debian11 \ --vcpu=2 \ --ram=4096 \ --disk path=/mnt/vms/production/domain.org.qcow2 \ --check path_in_use=off \ --graphics spice \ --location=/mnt/vms/isos/debian-12.4.0-amd64-netinst.iso \ --network bridge:br0 \ --initrd-inject /mnt/vms/cfgs/preseed.cfg
Other resources online insisted that I needed to add something like –extra-args=“ks=file:/mnt/vms/cfgs/preseed.cfg console=tty0 console=ttyS0,115200” to the recipe as well, but I found that that was only required for those desiring kickstarter and/or if they are using a remote site to host the configs from. My next task was to check the stock configuration file and create my own preseed config that would create machines as I desired. Here's the stock Debian config and the one I developed:
My next task was to automate all of this with a simple shell script. Here's what I came up with:
#!/bin/bash
echo -n "Please enter the fully qualified hostname: "
read hostname
echo -n "How large (in GB) would you like the virtual hard disk to be? "
read size
qemu-img create -f qcow2 /mnt/vms/production/${hostname}.qcow2 ${size}G
sleep 2s
echo -n "What do you want the last octet of the IP address for this host to be? "
read ip
sleep 2s
echo "Okay, I am now creating the preseed.cfg file for your host ..."
mkdir /mnt/vms/cfgs/external/${hostname}
cp -ar /mnt/vms/cfgs/external/preseed.cfg /mnt/vms/cfgs/external/${hostname}/preseed.cfg
rpl -w "unassigned-hostname" "$hostname" /mnt/vms/cfgs/external/${hostname}/preseed.cfg
rpl -w "unassigned-domain" "$hostname" /mnt/vms/cfgs/external/${hostname}/preseed.cfg
rpl -w "XXX" "$ip" /mnt/vms/cfgs/external/${hostname}/preseed.cfg
sleep 2s
echo "Alright, I am opening up virt-installer and building your host ..."
sleep 2s
virt-install --name=${hostname}.qcow2 \
--os-variant=debian11 \
--vcpu=2 \
--ram=4096 \
--disk path=/mnt/vms/production/${hostname}.qcow2 \
--check path_in_use=off \
--graphics spice \
--location=/mnt/vms/isos/debian-12.4.0-amd64-netinst.iso \
--network bridge:br0 \
--network bridge:virbr1 \
--initrd-inject /mnt/vms/cfgs/external/${hostname}/preseed.cfg
This script prompts me for domain name and size of the virtual hard disk. I will likely expand the script to add more parameters down the road, such as but not exclusive to networking, vdd location, ram, and so on. As I expand this, I will update the wiki here and also push my latest scripts and configs to the repository:
— oemb1905 2024/02/17 17:53
