This is a repo for etcd snapcraft; each directory corresponds to a release, snapcraft will create a snap of that release if run in that directory. etcd-master contains snapcraft.yaml to build a snap of upstream master. Ultimately etcd-master should land on the upstream master branch for automatic edge builds.
The ingest track snaps are to migrate data from classic Ubuntu / Debian etcd packaging, with configuration in /etc/default/etcd and data in /var/lib/etcd to the new snap location of /var/snap/etcd/ common and current. Install the snap with --channel=ingest/stable then run etcd.ingest before refreshing to channel=2.3/stable and validating the running and strictly confined etcd. It is then possible to upgrade to etcd 3.0 and 3.1 by switching to the relevant tracks.
It is advisable to backup the cluster in advance of this procedure.
The whole cluster must successfully complete each version jump - in other words, you must upgrade each member to the 2.3 track, and once the logs indicate that the cluster has switched to 2.3 mode, you can start upgrading the members to 3.0, and similarly then to 3.1 once the whole cluster is on 3.0.
So the process on a single node looks like this:
sudo snap install etcd --channel=ingest/stable sudo etcd.ingest
If all has gone smoothly you should see a prompt to refresh to the 2.3 track. Also, you should see the appropriate configuration files and key material in /var/snap/etcd/common and /var/snap/etcd/current
sudo snap refresh etcd --channel=2.3/stable
Your logs should now reflect this member joining the cluster. If all looks good, repeat the process on each member. When the final member is done you should see a log entry confirming the update of the cluster to 2.3.
sudo snap refresh etcd --channel=3.0/stable
Note that the 3.0 release of etcd changed the format of configuration to YAML, and the launch wrapper in the etcd 3.0 snap will determine if this migration needs to be done. If so you should havev a backup of the old 2.x config in /var/snap/etcd/common and the new yaml config in that directory as well. Logs should indicate the member joining the cluster.
Repeat on all members, and then the cluster should report being upgraded to support 3.0 capabilities.
Before you move on to 3.1, though, please make another backup of the cluster.
In etcd 3.1 the semantics of certificate names and validation seem to have been tightened appropriately. Existing certificates may fail to validate. Nevertheless, you can upgrade to 3.1 with:
sudo snap refresh etcd --channel=3.1/stable