Quickly clone/start/stop/run commands on/delete a VM.
This script can be used to quickly set up a VM based on a existing disk image, connect to the new VM via ssh and after you are done, throw the VM away.
This script was inspired by tools like vagrant, docker, etc. These allow you to quickly and deterministically create virtualized environments for development or experimentation. Unfortunately both have the "download and run code from somewhere on the internet" pattern baked deep into them. Unfortunately created base images for both is kind of bothersome. This script is supposed to bring some of this agility to libvirt.
First create a VM based on a existing base VM. Currently this creates a completely new VM with the first qcow2 image if the base-vm as a backing store for the newly created qcow2 image of testvm.
quickvm clone basevm testvm
and get a shell by ssh-ing into the testvm
quickvm shell testvm
or just execute a command (again via ssh)
quickvm shell testvm sudo pacman -S ruby
and then throw away the vm
quickvm trash testvm
It's also possible to transfer data from and to the VM
quickvm push testvm ./data /tmp/
quickvm pull testvm /var/log/whatever.log ./logs/
The default is to use rsync, with a fallback to scp if it isn't installed.
Per default quickvm executes ssh with your current username (i.e. $USER) you
can change this using the -u option (supported by a couple of commands):
quickvm shell -u root
or change the global default:
mkdir -p ~/.config/quickvm
echo "QUICKVM_USER=root" >> ~/.config/quickvm/config.sh
or change the default per VM:
quickvm setuser myvm root
Basically none except for libvirt and things that come with libvirt:
virsh, qemu-img, virt-install
- set internal options via command line parameters (this includes more sophisticated cli parsing)
- File sharing
- Make it easy to share files via 9p (if possible even in the face of SELinux)
- Template scripts to create VMs
- Execute a script that sets up a VM out of the blue
- Provisiong (vagrant style)
- copy files
- execute a shell script
- wget and execute a shell script
When using 9pfs you will run into permission problems, because the uids inside the guest and the host uids will not match. E.g. it happens that you create a file inside the guest, which will be owned by the qemu user. If you used the mapped setting in 9pfs, this means you will probably not be able to access this from inside the guest.
While the 9pfs problems would be solved if you'd use the user session, which starts the VMs as your local user, you will face other problems. See this vagrant-libvirt bug for some of the issues: vagrant-libvirt/vagrant-libvirt#272
The most impacting thing is that virsh domifaddr won't work anymore.
quickvm works around this be by directly parsing the file
/var/lib/libvirt/dnsmasq/virbr0.status.
Warning: some ranting ahead.
To be fair vagrant is already pretty close to what I want. Unfortunately it
doesn't play so well with libvirt.
- Doesn't work so well with
libvirt- Most base boxes don't work
- Throws away VM automatically if initial ssh fails, which is very annoying in combination with this bug.
- Creating base boxes is kind of annoying. packer works reasonably well.
Still most of the time I just want to log in and install a package or two
in my base VM. Using
vagrant packageall the time seems too much work to me. vagrant sshworks only in the same dir as theVagrantfile. I'd like this to work from any dir given an identifier.
- Containers don't contain. and I might want to run completely untrusted software. Load some kernel or pam module from the internet or wherever. I like to think the damage is somewhat minimal in a VM that is going to be thrown away 10 minutes later.
- Some things just can't be done inside unprivileged docker containers. For example chrooting, which is required on some distros for package building.
- Most container managment software has this app-centric view, while I want a interactive environment.