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Object Names and IDs | concept | 20 |
Each object in your cluster has a Name that is unique for that type of resource. Every Kubernetes object also has a UID that is unique across your whole cluster.
For example, you can only have one Pod named myapp-1234
within the same namespace, but you can have one Pod and one Deployment that are each named myapp-1234
.
For non-unique user-provided attributes, Kubernetes provides labels and annotations.
Names
{{< glossary_definition term_id="name" length="all" >}}
Below are three types of commonly used name constraints for resources.
DNS Subdomain Names
Most resource types require a name that can be used as a DNS subdomain name as defined in RFC 1123. This means the name must:
- contain no more than 253 characters
- contain only lowercase alphanumeric characters, '-' or '.'
- start with an alphanumeric character
- end with an alphanumeric character
DNS Label Names
Some resource types require their names to follow the DNS label standard as defined in RFC 1123. This means the name must:
- contain at most 63 characters
- contain only lowercase alphanumeric characters or '-'
- start with an alphanumeric character
- end with an alphanumeric character
Path Segment Names
Some resource types require their names to be able to be safely encoded as a path segment. In other words, the name may not be "." or ".." and the name may not contain "/" or "%".
Here’s an example manifest for a Pod named nginx-demo
.
apiVersion: v1
kind: Pod
metadata:
name: nginx-demo
spec:
containers:
- name: nginx
image: nginx:1.14.2
ports:
- containerPort: 80
{{< note >}} Some resource types have additional restrictions on their names. {{< /note >}}
UIDs
{{< glossary_definition term_id="uid" length="all" >}}
Kubernetes UIDs are universally unique identifiers (also known as UUIDs). UUIDs are standardized as ISO/IEC 9834-8 and as ITU-T X.667.
{{% heading "whatsnext" %}}
- Read about labels in Kubernetes.
- See the Identifiers and Names in Kubernetes design document.