etcdctl: The etcd Client

Get fluent in etcdctl — put and get keys, read whole prefixes, watch for changes live, tie keys to leases, run a compare-and-set, and inspect the cluster from the command line.

etcd is the consistent key-value store at the heart of Kubernetes and a hundred other systems, and etcdctl is how you talk to it from a terminal. It is a command-and-exit shell client: you type one command, it runs, it returns. We start from an empty keyspace and build up real fluency one small thing at a time — writing and reading keys, scanning a whole prefix, watching a key change in real time, attaching keys to leases so they expire on their own, doing an atomic compare-and-set, and finally checking the health and shape of the cluster itself. Each idea lands on its own command, the way you would actually run it.

What you'll build

• Put and get keys in the etcd keyspace
• Read whole subtrees with range reads over a prefix
• Delete single keys and prefixes
• Watch keys for live PUT and DELETE events
• Tie keys to leases so they expire automatically
• Run an atomic compare-and-set transaction
• Inspect cluster members, status and health

Contents

1. Write your first key
2. Read it back
3. Read just the value
4. Overwrite a key
5. See what an overwrite replaced
6. Add a few more keys
7. Read a whole prefix
8. List just the keys
9. Delete a key
10. Delete a whole prefix
11. Watch a key for changes
12. See the events arrive
13. Watch a whole subtree
14. Grant a lease
15. Attach a key to the lease
16. Check the time remaining
17. Set up for a compare-and-set
18. Run an atomic compare-and-set
19. Confirm the new value
20. Watch a compare fail
21. List the cluster members
22. Read endpoint status as a table
23. Check the cluster is healthy
24. Get machine-readable output