Equality and set selectors
- Docker & Kubernetes course
- Intermediate
- Lesson 65/82
- 4 min
Learn equality and set-based selectors.
Equality and set selectors
There are two kinds of selectors:
- Equality-based:
=,==,!=. - Set-based:
in,notin, existence (key) and absence (!key).
kubectl get pods -l 'ortam in (prod,staging)'
kubectl get pods -l 'katman notin (test)'
kubectl get pods -l 'surum' # those with a surum label
kubectl get pods -l 'app=web,ortam in (prod,staging),!eski'Since parentheses and exclamation marks have special meaning in the shell, the expression is quoted.
Counterparts in YAML
The set expressions on the command line correspond to matchExpressions operators in YAML:
# -l 'ortam in (prod,staging)'
- key: ortam
operator: In
values: [prod, staging]
# -l '!eski'
- key: eski
operator: DoesNotExist
# -l 'surum'
- key: surum
operator: ExistsPractice Set queries
Write three commands listing: the pods whose ortam is prod or staging; the pods whose katman isn't test; the pods without an eski label.
Starter code
# buraya yazSample solution
kubectl get pods -l 'ortam in (prod,staging)'
kubectl get pods -l 'katman notin (test)'
kubectl get pods -l '!eski'Expected output
NAME READY STATUS RESTARTS AGE web-7c5b9f6d8-abcde 1/1 Running 0 2h web-staging-9f8e7d 1/1 Running 0 1h
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Does the expression katman notin (test) select pods with no katman label at all?
- It errors
- Yes; notin also covers those without the key Correct answer
- No
- Only in the default namespace
Explanation: For only those that have the label and it isn't test, write katman,katman notin (test).
2 Select those whose value is in a set.
Question
kubectl get pods -l 'ortam ____ (prod,staging)'
Answer
kubectl get pods -l 'ortam in (prod,staging)'Explanation: in is a set-based operator.
3 Match.
| Term | Meaning |
|---|---|
in |
In |
notin |
NotIn |
anahtar |
Exists |
!anahtar |
DoesNotExist |