Usando o volume no Dockerfile

Exemplo não utilizando volume

Criação do Dockerfile sem utilizar volume:

/tmp/volume/volume$ ls
/tmp/volume/volume$ touch Dockerfile
/tmp/volume/volume$ vim Dockerfile
/tmp/volume/volume$ cat Dockerfile
FROM ubuntu:22.04
# VOLUME /app
WORKDIR /app

Construção da imagem:

$ docker image build -t ubuntu-volume -f Dockerfile .
[+] Building 12.2s (7/7) FINISHED                       docker:default
 => [internal] load build definition from Dockerfile              0.0s
 => => transferring dockerfile: 82B                               0.0s
 => [internal] load metadata for docker.io/library/ubuntu:22.04   3.3s
 => [auth] library/ubuntu:pull token for registry-1.docker.io     0.0s
 => [internal] load .dockerignore                                 0.0s
 => => transferring context: 2B                                   0.0s
 => [1/2] FROM docker.io/library/ubuntu:22.04@sha256:adbb90115a2  8.6s
 => => resolve docker.io/library/ubuntu:22.04@sha256:adbb90115a2  0.0s
 => => sha256:adbb90115a21969d2fe6fa7f9af4253e16 1.34kB / 1.34kB  0.0s
 => => sha256:075680e983398fda61b1ac59ad733ad81d18df 424B / 424B  0.0s
 => => sha256:53a843653cbcd9e10be207e951d907dc24 2.30kB / 2.30kB  0.0s
 => => sha256:857cc8cb19c0f475256df4b7709003b7 29.54MB / 29.54MB  7.4s
 => => extracting sha256:857cc8cb19c0f475256df4b7709003b77f10121  1.0s
 => [2/2] WORKDIR /app                                            0.1s
 => exporting to image                                            0.0s
 => => exporting layers                                           0.0s
 => => writing image sha256:fb0bf2bef8f7c519918810738a602e83f61b  0.0s
 => => naming to docker.io/library/ubuntu-volume                  0.0s
$ docker image ls ubuntu-volume
REPOSITORY      TAG       IMAGE ID       CREATED          SIZE
ubuntu-volume   latest    fb0bf2bef8f7   20 seconds ago   77.9MB 

Execução do container e criação de arquivo:

$ docker container run -it ubunt
u-volume /bin/bash
root@924bad832a21:/app#
root@924bad832a21:/app# ls
root@924bad832a21:/app# touch teste1.txt
root@924bad832a21:/app# ls
teste1.txt

Em outro terminal é possível verificar que nenhum volume foi criado:

$ docker volume ls
DRIVER    VOLUME NAME

Saída do container:

root@924bad832a21:/app# exit

Exemplo utilizando volume sem mapeamento

Alteração do Dockerfile para utilizar volume:

/tmp/volume/volume$ vim Dockerfile
/tmp/volume/volume$ cat Dockerfile
FROM ubuntu:22.04
VOLUME /app
WORKDIR /app

Construção da imagem:

/tmp/volume/volume$ docker image build -t ubuntu-volume -f Dockerfile .
[+] Building 1.9s (7/7) FINISHED                        docker:default
 => [internal] load build definition from Dockerfile              0.0s
 => => transferring dockerfile: 80B                               0.0s
 => [internal] load metadata for docker.io/library/ubuntu:22.04   1.8s
 => [auth] library/ubuntu:pull token for registry-1.docker.io     0.0s
 => [internal] load .dockerignore                                 0.0s
 => => transferring context: 2B                                   0.0s
 => [1/2] FROM docker.io/library/ubuntu:22.04@sha256:adbb90115a2  0.0s
 => CACHED [2/2] WORKDIR /app                                     0.0s
 => exporting to image                                            0.0s
 => => exporting layers                                           0.0s
 => => writing image sha256:beb3081df225027b6939d1b58f569c1d74e5  0.0s
 => => naming to docker.io/library/ubuntu-volume                  0.0s

Inspeção da imagem criada:

/tmp/volume/volume$ docker image inspect ubuntu-volume
...
            "Volumes": {
                "/app": {}
            },
...

Execução do container:

/tmp/volume/volume$ docker container run -it ubuntu-volume /bin/bash
root@a2fdfb0bc904:/app# ls

Criação de arquivo:

root@a2fdfb0bc904:/app# touch teste1.txt
root@a2fdfb0bc904:/app# ls
teste1.txt
root@a2fdfb0bc904:/app#

Verificação do volume criado:

$ docker volume ls
DRIVER    VOLUME NAME
local     ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f

Saída do container:

root@a2fdfb0bc904:/app# exit
exit
/tmp/volume/volume$

Inspeção do volume:

marcelo@Latitude5440:/tmp/volume/volume$ docker volume ls
DRIVER    VOLUME NAME
local     ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f
/tmp/volume/volume$ docker volume inspect ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f
[
    {
        "CreatedAt": "2024-08-25T13:45:06-03:00",
        "Driver": "local",
        "Labels": {
            "com.docker.volume.anonymous": ""
        },
        "Mountpoint": "/var/lib/docker/volumes/ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f/_data",
        "Name": "ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f",
        "Options": null,
        "Scope": "local"
    }
]
/tmp/volume/volume$ sudo tree /var/lib/docker/volumes/ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f/_data
[sudo] password for marcelo:
/var/lib/docker/volumes/ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f/_data
└── teste1.txt

0 directories, 1 file

Criação de outro container e arquivo:

/tmp/volume/volume$ docker container run -it ubuntu-volume /bin/bash
root@52156328f538:/app# ls
root@52156328f538:/app# touch teste2.txt
root@52156328f538:/app# ls
teste2.txt
root@52156328f538:/app#

Um novo volume foi criado:

$ docker volume ls
DRIVER    VOLUME NAME
local     17e2f044f185afc45705ca5a18ac893c0abf65fb216b0a4a12182dbd4cdc449f
local     ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f

Inspeção do novo volume:

$ sudo tree /var/lib/docker/volumes/17e2f044f185afc45705ca5a18ac893c0abf65fb216b0a4a12182dbd4cdc449f
/var/lib/docker/volumes/17e2f044f185afc45705ca5a18ac893c0abf65fb216b0a4a12182dbd4cdc449f
└── _data
    └── teste2.txt

1 directory, 1 file

Exemplo utilizando volume com mapeamento

/tmp/volume/volume$ docker container run -it -v ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f:/app ubuntu-volume /bin/bash
root@7f06006f1374:/app# ls
teste1.txt

$ docker container inspect 7f06006f1374
...
        "Mounts": [
            {
                "Type": "volume",
                "Name": "ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f",
                "Source": "/var/lib/docker/volumes/ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f/_data",
                "Destination": "/app",
                "Driver": "local",
                "Mode": "z",
                "RW": true,
                "Propagation": ""
            }
        ],
...

$ docker inspect volume
[
    {
        "CreatedAt": "2024-08-25T13:45:06-03:00",
        "Driver": "local",
        "Labels": {
            "com.docker.volume.anonymous": ""
        },
        "Mountpoint": "/var/lib/docker/volumes/ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f/_data",
        "Name": "ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f",
        "Options": null,
        "Scope": "local"
    }
]

$ sudo tree /var/lib/docker/volumes/ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f/
/var/lib/docker/volumes/ea53a4f651c1bfd71a90349ad6e56295a631db38815478dd0e882edf81d5b86f/
└── _data
    └── teste1.txt

1 directory, 1 file