#devbox

devbox is a simple makefile that generates disk images and libvirt domains. It is little more than a set of carefully crafted virt-builder and virt-install commands. Creating a domain is as simple as running make with a few variables defined, either in a secondary Makefile or on the command line. But first, some initial set up steps must be taken.

#Getting started

The init.sh script need only run once. The script assumes a Fedora Workstation host; adjust as needed. It will install the necessary packages, add libvirt NSS modules to /etc/nsswitch.conf, and create a storage pool for storing domain volumes. The storage volume path is hard-coded to /var/lib/libvirt/pools/pool0 (if you change it in init.sh, you'll need to adjust lib.mk too). You can set up either a filesytem storage pool or a plain directory storage pool. Set POOL_TYPE when running init.sh to select the storage pool type. If you set POOL_TYPE to fs, you must specify a source device path in the SOURCE_DEV variable. For example, to use an existing device, /dev/sdc, as a filesystem storage pool, run: POOL_TYPE=fs SOURCE_DEV=/dev/sdc bash init.sh. Or to use a directory: POOL_TYPE=dir bash init.sh. There is no default POOL_TYPE value. You must choose.

If your host use SELinux for access control, you will need to relabel the directory you mount into guests with a type that can be accessed by the system account that runs qemu.

For example, to export $HOME/Projects to guests, you will need to first recursively relabel that directory:

sudo semanage fcontext --add --type svirt_home_t '/home/[^/]+/Projects(/.*)?'
sudo restorecon -Rv $HOME/Projects

Then set the CODE_DIR make variable when installing a domain.

make -f fedora-34.mk CODE_DIR=$HOME/Projects install-fedora-34

#Usage

"devbox" domains can be created by creating a .mk and .txt.in file (see fedora-34.mk and fedora-34.txt.in as examples). The .txt.in file is use as the value to the --commands-from-file argument to virt-builder. See man virt-builder for details. The .mk file is a simple makefile that defines some concrete targets. These targets will be fulfilled by generic targets defined in lib.mk.

For example, to add a centos-8 domain, create a centos-8.mk and populate with the correct values:

cat > centos-8.mk << EOF
include lib.mk

.PHONY: install
install: install-centos-8

.PHONY: uninstall
uninstall: uninstall-centos-8

# Name of the image according to virt-builder
centos-8.qcow2: OS_VERSION = centos-8.2

# Desired hostname of the guest
centos-8.qcow2 centos-8.xml install-centos-8 uninstall-centos-8: HOSTNAME = centos-8

# Name of the variant to use according to `osinfo-query os`
centos-8.xml:   OS_VARIANT = centos8
EOF

And populate centos-8.txt.in with virt-builder customization arguments:

cat > centos-8.txt.in << EOF
root-password password:fedora

install automake,autoconf,git,jq,make,sudo,vim,wget
update

run-command useradd --groups wheel --create-home --password "" @USER@; passwd --delete @USER@
ssh-inject @USER@

timezone @TIMEZONE@
append-line /etc/fstab:/code /code virtiofs defaults 0 0
selinux-relabel
EOF

Now run create and install the domain with make -f centos-8.mk install. Once the domain has been created, access it either by attaching directly to the console (virsh console centos-8) or connecting over SSH (ssh centos-8). Once logged in, the CODE_DIR defined above will have been exported to the guest and mounted to the path /code. Any changes made to the CODE_DIR on the host will immediately be reflected in the guest, and vice versa.