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Scripts and utilities to install and manage KVM machines

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Introduction

Scripts to conveniently install and manage multiple KVM machines.

During development or, in particular, when I'm trying to reproduce bugs I often find I need a group of machines that need to be quickly provisioned and isolated from whatever I was currently doing. These machines typically need identical configuration (i.e., ram & disk & network). I also require a naming pattern so that when I run virsh list I can actually recall why I spun them up in the first place.

The scripts in this repository allow you to:

  • provision KVM-based machines, based on a profile
  • manage those machines (reboot, shutdown, start)
  • take snapshots
  • delete snapshots
  • revert to a particular snapshot
  • upload images to the KVM storage pool

Profiles

To manage disparate configurations we have the notion of a profile. A profile is a just a file with per-profile properties.

Example

$ cat kup-centos7
export KUP_PREFIX=centos7
export KUP_NETWORK=k8s
export KUP_DOMAINNAME=k8s.home
# https://cloud.centos.org/centos/7/images/CentOS-7-x86_64-GenericCloud.qcow2
export KUP_CLOUD_IMG=CentOS-7-x86_64-GenericCloud.qcow2
export KUP_OS_VARIANT=rhel7.4
export KUP_CLOUD_USERNAME=centos

Taking these environment variables in turn we have:

  • KUP_PREFIX - the prefix for machine names; machines will be provisioned as $KUP_PREFIX-vm-$N.
  • KUP_NETWORK - the libvirt network; this needs to be provisioned ahead of time and it also needs to be started/running
  • KUP_DOMAINNAME the domain the KVM machine resides in. This is passed as meta-data to cloud-init.
  • KUP_CLOUD_IMG - the image to clone for the new machine
  • KUP_CLOUD_USERNAME - the cloud-image user name
  • KUP_OS_VARIANT - optional; helper for libvirt

RHEL 7.4 Example

$ cat kup-rhel74
export KUP_PREFIX=rhel74-dev
export KUP_NETWORK=k8s
export KUP_DOMAINNAME=k8s.home
export KUP_CLOUD_IMG=rhel-server-7.4-x86_64-kvm.qcow2
export KUP_OS_VARIANT=rhel7.4
export KUP_CLOUD_USERNAME=cloud-user

Fedora 27 Example

$ cat kup-fedora27
export KUP_PREFIX=fedora27-dev
export KUP_NETWORK=k8s
export KUP_DOMAINNAME=k8s.home
# https://download.fedoraproject.org/pub/fedora/linux/releases/27/CloudImages/x86_64/images/Fedora-Cloud-Base-27-1.6.x86_64.qcow2
export KUP_CLOUD_IMG=Fedora-Cloud-Base-27-1.6.x86_64.qcow2
export KUP_OS_VARIANT=fedora26	# no variant in libvirt (ATM) for fedora27
export KUP_CLOUD_USERNAME=fedora

Debian Example

$ cat kup-debian9
export KUP_PREFIX=debian9
export KUP_NETWORK=k8s
export KUP_DOMAINNAME=k8s.home
export KUP_CLOUD_IMG=debian-9.3.5-20180213-openstack-amd64.qcow2
export KUP_OS_VARIANT=linux	# no variant in libvirt (ATM)
export KUP_CLOUD_USERNAME=debian

Building a Cluster

To build a cluster based on a profile run:

$ KUP_ENV=$HOME/kup-centos7 kup-domain-install 1
adding pubkey from /home/aim/.ssh/id_rsa.pub
adding user data from /usr/local/bin/../libexec/kvm-cluster-up/user-data
generating configuration image at /tmp/tmp.6xVhuYVKeN/centos7-vm-1-ds.iso
Pool default refreshed
Vol centos7-vm-1-ds.iso created
Vol centos7-vm-1.qcow2 cloned from CentOS-7-x86_64-GenericCloud.qcow2
Size of volume 'centos7-vm-1.qcow2' successfully changed to +50G
Pool default refreshed
Starting install...
Domain creation completed.

This provisions and boots asynchronously. The default action is to boot the machine, let cloud-init run, then power off. I chose to power-off as the default to facilitate snapshots. The provisioning step dynamically creates a cloud-init data-store as an ISO and attaches that disk as /dev/vdb. That disk needs to be detached if you want to use snapshots.

But one machine does not make a cluster! In general all the kup-* scripts take instance-id arguments, where an instance-id is just a unique symbol.

To provision multiple machines:

$ KUP_ENV=$HOME/kup-centos7 kup-domain-install 1 2 3 4

$ virsh list --all | grep centos7-vm
13 centos7-vm-2 running
14 centos7-vm-3 running
15 centos7-vm-4 running
16 centos7-vm-1 running

To provision more machines:

$ KUP_ENV=$HOME/kup-centos7 kup-domain-install 80 90 100

The numbers do not need to be consecutive; they are just used to provide unique names. In fact, they don't even need to be numbers.

$ KUP_ENV=$HOME/kup-centos7 kup-domain-install master etcd node1 node2 node3

$ virsh list --all
Id    Name                           State
----------------------------------------------------
-     centos7-vm-1                   shut off
-     centos7-vm-2                   shut off
-     centos7-vm-3                   shut off
-     centos7-vm-4                   shut off
-     centos7-vm-master              shut off
-     centos7-vm-etcd                shut off
-     centos7-vm-node1               shut off
-     centos7-vm-node2               shut off
-     centos7-vm-node3               shut off

Memorable Profiles

Sometimes I find I have a number of centos7 machines already running that should not be perturbed but I need moar to investigate a different bug so let's just create new instances...

$ KUP_ENV=$HOME/kup-centos7 10 20 30

But relying on different sets of numbers can get confusing; it's easier to create another profile with a prefix that has more context:

$ cat kup-centos7-bz18020
export KUP_PREFIX=centos7-bz18020
export KUP_NETWORK=k8s
export KUP_DOMAINNAME=k8s.home
export KUP_CLOUD_IMG=CentOS-7-x86_64-GenericCloud.qcow2
export KUP_OS_VARIANT=rhel7.4
export KUP_CLOUD_USERNAME=centos

Exporting KUP_ENV

Here be dragons

You can export KUP_ENV which means you don't have to prefix any of the kup-*<program>* usage:

$ export KUB_ENV=$HOME/kup-centos7
# Boot a machine
$ kup-domain-install 1
# Do lots of work in another shell, lunch, ...

# Come back from lunch...
$ kup-domain-delete 1
# **OOPS!** This wasn't the profile I thought I was using... Dang! IRL, way too often. :/

Accessing the machines

As I only use cloud-based images you need to use the correct username when accessing the machines. This is also why you need to specify KUP_CLOUD_USERNAME in the profile. I wrap up access in my $HOME/.ssh/config:

Host *
	GSSAPIAuthentication no
	CanonicalizeHostname yes

Host centos7-vm-1 centos7-vm-2 centos7-vm-3 centos7-vm-4 centos7-vm-5 centos7-vm-6 centos7-vm-7 centos7-vm-8
	HostName %h.k8s.home
	User centos

Host rhel74-vm-1 rhel74-vm-2 rhel74-vm-3 rhel74-vm-4 rhel74-vm-5 rhel74-vm-6 rhel74-vm-7 rhel74-vm-8
	HostName %h.k8s.home
	User cloud-user

Host fedora27-vm-1 fedora27-vm-2 fedora27-vm-3 fedora27-vm-4 fedora27-vm-5 fedora27-vm-6 fedora27-vm-7 fedora27-vm-8
	HostName %h.k8s.home
	User cloud-user

Host *.k8s.home
	GSSAPIAuthentication no
	ControlPersist 10m
	ControlMaster auto
	ControlPath /tmp/%r@%h:%p
	ForwardAgent yes
	StrictHostKeyChecking no
	UserKnownHostsFile /dev/null
	HashKnownHosts no
	LogLevel QUIET
	CheckHostIP no

Note: as these machines are on my LAN and tend to have a short-life, the security setup is, well, super-lax! I could also use wildcards but then tab completion wouldn't work.

Logging into the instance

Based on the previous .ssh/config we can login straight in without having to worry about what the user name should be.

$ ssh centos7-vm-1
$ ssh rhel74-vm-2
$ ssh fedora27-vm-3

You can also login via the console:

$ virsh dominfo centos7-vm-1 | grep Id: | awk '{ print $2 }'
# 19
$ virsh console 19
Connected to domain centos7-vm-1
Escape character is ^]

CentOS Linux 7 (Core)
Kernel 3.10.0-693.el7.x86_64 on an x86_64
centos7-vm-1 login: centos
Password: password

Last login: Wed Feb 21 11:19:23 from 192.168.30.64

I told you the security was super-lax!

Machine management

There are a number of scripts to aid in provisioning, starting up, shutting down and rebooting the machines in the cluster.

  • kup-domain-delete
  • kup-domain-install
  • kup-domain-reboot
  • kup-domain-start
  • kup-domain-stop
  • kup-domain-ipaddr

Each script takes <instance-id>... as [the only] arguments. Hopefully these are all very obvious and orthogonal.

$ kup-domain-delete 1 2 3 4
$ kup-domain-delete node1 etcd
$ kup-domain-install 1 2 3 4
$ kup-domain-reboot 82 90 91
$ kup-domain-reboot master
$ kup-domain-start 1 2 3 4
$ kup-domain-start master etcd node1 node2
$ kup-domain-stop  master etcd node1 node2
$ kup-domain-ipaddr master etcd node1 node2

Snapshots

Reinstalling is not for fun or profit! Well, not normally. To speed up my dev-cycle I tend to make liberal use of snapshots.

Install base image and detach config-drive

$ kup-domain-install 1 2 3 4
# wait for machine(s) to provision and power off
$ kup-detach-config-drive 1 2 3 4
Disk detached successfully
Disk detached successfully
Disk detached successfully
Disk detached successfully

Take a snapshot

Prep the machine(s) in some way, then take a snapshot so we can eaily revert:

$ SNAPSHOT=baseinstall kup-snapshot-create 1
Domain snapshot baseinstall created

$ kup-domain-start 1
Domain centos7-vm-1 started

$ ansible-playbook -i centos7-vm-1, /path/to/playbook.yaml

$ kup-domain-stop 1
Domain centos7-vm-1 destroyed

$ SNAPSHOT=pkg-refresh kup-snapshot-create 1
Domain snapshot pkg-refresh created

List snapshots

$ kup-snapshot-list 1 2 3 4

Name                 Creation Time             State
------------------------------------------------------------
baseinstall          2018-02-21 11:43:01 +0000 shutoff
pkg-refresh          2018-02-21 11:43:40 +0000 shutoff

Name                 Creation Time             State
------------------------------------------------------------

Name                 Creation Time             State
------------------------------------------------------------

Name                 Creation Time             State
------------------------------------------------------------

Here you can see I've only created snapshots for the machine identified as 1. But really the whole point of these scripts is to take the same action against multiple machines:

$ SNAPSHOT=baseinstall kup-snapshot-create 1 2 3 4
Domain snapshot baseinstall created
Domain snapshot baseinstall created
Domain snapshot baseinstall created
Domain snapshot baseinstall created

Reverting/Selecting a snapshot by name

$ kup-domain-stop 1
$ SNAPSHOT=baseinstall kup-snapshot-select 1
$ kup-domain-start 1

Updating a snapshot

$ kup-domain-stop 1
$ SNAPSHOT=baseinstall kup-snapshot-select 1
# Start from a known-good place.
$ kup-domain-start 1

# login, do some corrections in "baseinstall", then snapshot again.
$ kup-domain-stop 1
$ SNAPSHOT=pkg-refresh kup-snapshot-replace 1

Installation

Please read the INSTALL companion.

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Scripts and utilities to install and manage KVM machines

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