birsh

birsh is a replacement to libvirt but in bash and without XML files (and with many less features, I admit) :)

I created this bash script to be able to quickly start virtual machines with KVM or systemd-nspawn (more or less container mode) on my laptop without playing with ton of XML files or an awful GUI tool.

The second mode is useful if you want to boot only one virtual machine without network needs (here the network is shared with the host) like quick test of a patch, build or software. The first mode can be used as many times as you want.

This tool lacks features at this time like graphical screen, removable media boot, disk management and the code is not necessarily beautiful but it works for me :) (and you can contribute)

Installation

Just make install

Configuration

The main configuration file is /etc/birsh/settings and let you set the following items:

• IMAGESFOLDER: folder containing all disks
• MOUNTFOLDER: folder where to mount disks (for nspawn)
• TMPFOLDER: folder to put monitor sockets and temporary files (for start)
• BRIDGE: network device name for the bridge (for start)
• BRIDGEUP: optional setting to specify commands to execute after the bridge is up (eg. DHCP server)
• GATEWAY: network address of the host
• NETWORK: network to use for virtual machines (used for NAT)

The tool will automatically set NAT using iptables and create a /24 private network.

Requirements

You must have these tools installed on your host: brctl, ip, iptables, qemu-nbd, kpartx, socat, screen, systemd-nspawn (optional).

screen is used to give you an access to the serial console of a KVM virtual machine. You should set console=ttyS0 on the virtual machine's kernel boot argument to be able to use this feature.

qemu-nbd and kpartx are used for the nspawn mode.

Usage

birsh command [options]

Commands

birsh start name -m size [-g] [-s num] [-cdrom filename]
Start a new virtual machine using qemu-kvm. Return the QEMU monitor socket.

• name (mandatory): name of the disk to boot on
• -m size (mandatory): set size MB of memory to the virtual machine
• -g: enable graphical output
• -s num: set num CPUs to the virtual machine
• -cdrom filename: add filename (must be in IMAGESFOLDER/media) as a media and boot on it

birsh nspawn name
Start a new container using systemd-nspawn. Return a chrooted shell.

• name (mandatory): name of the disk to boot on

birsh serial name
Attach a screen to the serial console of a virtual machine (only for qemu-kvm)

• name (mandatory): name of the disk to attach console on

birsh list [base]
List all available qcow2 disk files in IMAGESFOLDER. Files in subfolders are excluded.

• base: list all images in IMAGESFOLDER/base

Examples

I consider you have some bootable disks in your IMAGESFOLDER, for example ubuntu.qcow2, exherbo.qcow2 and php.qcow2.

Boot the php virtual machine using qemu-kvm with 512 MB of memory:

birsh start php -m 512

Note: this command will output a prompt to the QEMU monitor socket. Typing quit in this monitor or powering off the virtual machine will release the socket and destroy the machine.

Attach to the php serial console (after birsh start php):

birsh serial php

Spawn a container for the disk exherbo:

birsh nspawn exherbo

Note: this command will mount the disk exherbo.qcow2 in MOUNTFOLDER/exherbo and boot it.

License

This tool is released under the ISC license. See the LICENSE file for more information.