Equality and set selectors

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: Exists

Exercise 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.

Show example solution

kubectl get pods -l 'ortam in (prod,staging)'
kubectl get pods -l 'katman notin (test)'
kubectl get pods -l '!eski'

Test yourself

Does the expression katman notin (test) select pods with no katman label at all?
- It errors
- Yes; notin also covers those without the key
- No
- Only in the default namespace
Show answer

Yes; notin also covers those without the key — For only those that have the label and it isn't test, write katman,katman notin (test).

Select those whose value is in a set.

kubectl get pods -l 'ortam ____ (prod,staging)'

Show answer

kubectl get pods -l 'ortam in (prod,staging)'

Match.

in

In
notin

NotIn
anahtar

Exists
!anahtar

DoesNotExist

Next lesson: Summary - Labels

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