mirror of
https://github.com/jpetazzo/container.training.git
synced 2026-05-11 03:16:35 +00:00
88 lines
1.7 KiB
Markdown
88 lines
1.7 KiB
Markdown
# Labels
|
|
|
|
* Labels allow to attach arbitrary metadata to containers.
|
|
|
|
* Labels are key/value pairs.
|
|
|
|
* They are specified at container creation.
|
|
|
|
* You can query them with `docker inspect`.
|
|
|
|
* They can also be used as filters with some commands (e.g. `docker ps`).
|
|
|
|
---
|
|
|
|
## Using labels
|
|
|
|
Let's create a few containers with a label `owner`.
|
|
|
|
```bash
|
|
docker run -d -l owner=alice nginx
|
|
docker run -d -l owner=bob nginx
|
|
docker run -d -l owner nginx
|
|
```
|
|
|
|
We didn't specify a value for the `owner` label in the last example.
|
|
|
|
This is equivalent to setting the value to be an empty string.
|
|
|
|
---
|
|
|
|
## Querying labels
|
|
|
|
We can view the labels with `docker inspect`.
|
|
|
|
```bash
|
|
$ docker inspect $(docker ps -lq) | grep -A3 Labels
|
|
"Labels": {
|
|
"maintainer": "NGINX Docker Maintainers <docker-maint@nginx.com>",
|
|
"owner": ""
|
|
},
|
|
```
|
|
|
|
We can use the `--format` flag to list the value of a label.
|
|
|
|
```bash
|
|
$ docker inspect $(docker ps -q) --format 'OWNER={{.Config.Labels.owner}}'
|
|
```
|
|
|
|
---
|
|
|
|
## Using labels to select containers
|
|
|
|
We can list containers having a specific label.
|
|
|
|
```bash
|
|
$ docker ps --filter label=owner
|
|
```
|
|
|
|
Or we can list containers having a specific label with a specific value.
|
|
|
|
```bash
|
|
$ docker ps --filter label=owner=alice
|
|
```
|
|
|
|
---
|
|
|
|
## Use-cases for labels
|
|
|
|
|
|
* HTTP vhost of a web app or web service.
|
|
|
|
(The label is used to generate the configuration for NGINX, HAProxy, etc.)
|
|
|
|
* Backup schedule for a stateful service.
|
|
|
|
(The label is used by a cron job to determine if/when to backup container data.)
|
|
|
|
* Service ownership.
|
|
|
|
(To determine internal cross-billing, or who to page in case of outage.)
|
|
|
|
* etc.
|
|
|
|
???
|
|
|
|
:EN:- Using labels to identify containers
|
|
:FR:- Étiqueter ses conteneurs avec des méta-données
|