Instalar y usar Dockers en Centos 7

Raul Unzue Pulido 11 abril, 2017 Linux, Virtualizacion Deja un comentario 11,030 Vistas

Instalar y usar Dockers en Centos 7

Hace un tiempo os enseñamos lo que era un Docker y como lanzarlos en vuestra nas Synology.

Cada vez que hago un laboratorio con dockers les veo mayor utilidad. Y es muy probable que para esta web y para otras que tengo construidas, migre todo a Dockers. Así que en esas cábalas me encuentro y os muestro como hacer una primera instalación en un servidor Centos 7. En este caso una máquina virtual que tengo en mi laboratorio VMware.

INSTALACION DOCKER CENTOS 7

Empezamos con la instalación, yo lo hago como root que para eso es un laboratorio:

[root@localhost ~]# curl -fsSL https://get.docker.com/ | sh

1	[root@localhost ~]# curl -fsSL https://get.docker.com/ \| sh

Para usar docker como otro usuario:

sudo usermod -aG docker your-user

1	sudo usermod -aG docker your-user

Arrancamos el servicio:

systemctl start docker

1	systemctl start docker

Verificamos que arranca correctamente:

[root@localhost ~]# systemctl status docker
● docker.service - Docker Application Container Engine
 Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; vendor prese t: disabled)
 Active: active (running) since mar 2017-04-11 15:54:20 CEST; 2s ago
 Docs: https://docs.docker.com
 Main PID: 2893 (dockerd)
 Memory: 15.3M
 CGroup: /system.slice/docker.service
 ├─2893 /usr/bin/dockerd
 └─2896 docker-containerd -l unix:///var/run/docker/libcontainerd/d...

abr 11 15:54:19 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:1...
abr 11 15:54:19 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:1...
abr 11 15:54:19 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:1...
abr 11 15:54:19 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:1...
abr 11 15:54:19 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:1...
abr 11 15:54:20 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:2...
abr 11 15:54:20 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:2...
abr 11 15:54:20 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:2...
abr 11 15:54:20 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:2...
abr 11 15:54:20 localhost.localdomain systemd[1]: Started Docker Application ...
Hint: Some lines were ellipsized, use -l to show in full.

[root@localhost ~]# systemctl status docker

● docker.service - Docker Application Container Engine

Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; vendor prese t: disabled)

Active: active (running) since mar 2017-04-11 15:54:20 CEST; 2s ago

Docs: https://docs.docker.com

Main PID: 2893 (dockerd)

Memory: 15.3M

CGroup: /system.slice/docker.service

├─2893 /usr/bin/dockerd

└─2896 docker-containerd -l unix:///var/run/docker/libcontainerd/d...

abr 11 15:54:19 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:1...

abr 11 15:54:20 localhost.localdomain dockerd[2893]: time="2017-04-11T15:54:2...

abr 11 15:54:20 localhost.localdomain systemd[1]: Started Docker Application ...

Hint: Some lines were ellipsized, use -l to show in full.

Habilitamos docker para que se ejecute en el arranque:
 [root@localhost ~]# systemctl enable docker
 Created symlink from /etc/systemd/system/multi-user.target.wants/docker.service to /usr/lib/systemd/system/docker.service.

Habilitamos docker para que se ejecute en el arranque:

[root@localhost ~]# systemctl enable docker

Created symlink from /etc/systemd/system/multi-user.target.wants/docker.service to /usr/lib/systemd/system/docker.service.

Pues ya está…¿no ha sido difícil no?

Ahora vamos a jugar un poco con lo que hemos instalado.

PRIMEROS PASOS CON DOCKERS EN CENTOS 7

Ahora los comandos que hay que utilizar pasan por una sentencia parecida a ésta:

docker [option] [command] [arguments]

1	docker [option] [command] [arguments]

Para revisar todos los subcomandos de los que disponemos:

[root@localhost ~]# docker

Usage: docker COMMAND

A self-sufficient runtime for containers

Options:
 --config string Location of client config files (default "/root/.docker")
 -D, --debug Enable debug mode
 --help Print usage
 -H, --host list Daemon socket(s) to connect to (default [])
 -l, --log-level string Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")
 --tls Use TLS; implied by --tlsverify
 --tlscacert string Trust certs signed only by this CA (default "/root/.docker/ca.pem")
 --tlscert string Path to TLS certificate file (default "/root/.docker/cert.pem")
 --tlskey string Path to TLS key file (default "/root/.docker/key.pem")
 --tlsverify Use TLS and verify the remote
 -v, --version Print version information and quit

Management Commands:
 container Manage containers
 image Manage images
 network Manage networks
 node Manage Swarm nodes
 plugin Manage plugins
 secret Manage Docker secrets
 service Manage services
 stack Manage Docker stacks
 swarm Manage Swarm
 system Manage Docker
 volume Manage volumes

Commands:
 attach Attach to a running container
 build Build an image from a Dockerfile
 commit Create a new image from a container's changes
 cp Copy files/folders between a container and the local filesystem
 create Create a new container
 diff Inspect changes to files or directories on a container's filesystem
 events Get real time events from the server
 exec Run a command in a running container
 export Export a container's filesystem as a tar archive
 history Show the history of an image
 images List images
 import Import the contents from a tarball to create a filesystem image
 info Display system-wide information
 inspect Return low-level information on Docker objects
 kill Kill one or more running containers
 load Load an image from a tar archive or STDIN
 login Log in to a Docker registry
 logout Log out from a Docker registry
 logs Fetch the logs of a container
 pause Pause all processes within one or more containers
 port List port mappings or a specific mapping for the container
 ps List containers
 pull Pull an image or a repository from a registry
 push Push an image or a repository to a registry
 rename Rename a container
 restart Restart one or more containers
 rm Remove one or more containers
 rmi Remove one or more images
 run Run a command in a new container
 save Save one or more images to a tar archive (streamed to STDOUT by default)
 search Search the Docker Hub for images
 start Start one or more stopped containers
 stats Display a live stream of container(s) resource usage statistics
 stop Stop one or more running containers
 tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE
 top Display the running processes of a container
 unpause Unpause all processes within one or more containers
 update Update configuration of one or more containers
 version Show the Docker version information
 wait Block until one or more containers stop, then print their exit codes

Run 'docker COMMAND --help' for more information on a command.

[root@localhost ~]# docker

Usage: docker COMMAND

A self-sufficient runtime for containers

Options:

--config string Location of client config files (default "/root/.docker")

-D, --debug Enable debug mode

--help Print usage

-H, --host list Daemon socket(s) to connect to (default [])

-l, --log-level string Set the logging level ("debug"|"info"|"warn"|"error"|"fatal") (default "info")

--tls Use TLS; implied by --tlsverify

--tlscacert string Trust certs signed only by this CA (default "/root/.docker/ca.pem")

--tlscert string Path to TLS certificate file (default "/root/.docker/cert.pem")

--tlskey string Path to TLS key file (default "/root/.docker/key.pem")

--tlsverify Use TLS and verify the remote

-v, --version Print version information and quit

Management Commands:

container Manage containers

image Manage images

network Manage networks

node Manage Swarm nodes

plugin Manage plugins

secret Manage Docker secrets

service Manage services

stack Manage Docker stacks

swarm Manage Swarm

system Manage Docker

volume Manage volumes

Commands:

attach Attach to a running container

build Build an image from a Dockerfile

commit Create a new image from a container's changes

cp Copy files/folders between a container and the local filesystem

create Create a new container

diff Inspect changes to files or directories on a container's filesystem

events Get real time events from the server

exec Run a command in a running container

export Export a container's filesystem as a tar archive

history Show the history of an image

images List images

import Import the contents from a tarball to create a filesystem image

info Display system-wide information

inspect Return low-level information on Docker objects

kill Kill one or more running containers

load Load an image from a tar archive or STDIN

logout Log out from a Docker registry

logs Fetch the logs of a container

pause Pause all processes within one or more containers

port List port mappings or a specific mapping for the container

ps List containers

pull Pull an image or a repository from a registry

push Push an image or a repository to a registry

rename Rename a container

restart Restart one or more containers

rm Remove one or more containers

rmi Remove one or more images

run Run a command in a new container

save Save one or more images to a tar archive (streamed to STDOUT by default)

search Search the Docker Hub for images

start Start one or more stopped containers

stats Display a live stream of container(s) resource usage statistics

stop Stop one or more running containers

tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE

top Display the running processes of a container

unpause Unpause all processes within one or more containers

update Update configuration of one or more containers

version Show the Docker version information

wait Block until one or more containers stop, then print their exit codes

Run 'docker COMMAND --help' for more information on a command.

Ahora vamos a comprobar que somos capaces de descargar imágenes. Prueba tonta:

[root@localhost ~]# docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
78445dd45222: Pull complete
Digest: sha256:c5515758d4c5e1e838e9cd307f6c6a0d620b5e07e6f927b07d05f6d12a1ac8d7
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://cloud.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/engine/userguide/

[root@localhost ~]# docker run hello-world

Unable to find image 'hello-world:latest' locally

latest: Pulling from library/hello-world

78445dd45222: Pull complete

Digest: sha256:c5515758d4c5e1e838e9cd307f6c6a0d620b5e07e6f927b07d05f6d12a1ac8d7

Status: Downloaded newer image for hello-world:latest

Hello from Docker!

This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:

1. The Docker client contacted the Docker daemon.

2. The Docker daemon pulled the "hello-world" image from the Docker Hub.

3. The Docker daemon created a new container from that image which runs the

executable that produces the output you are currently reading.

4. The Docker daemon streamed that output to the Docker client, which sent it

to your terminal.

To try something more ambitious, you can run an Ubuntu container with:

$ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:

https://cloud.docker.com/

For more examples and ideas, visit:

https://docs.docker.com/engine/userguide/

Si queremos buscar imágenes nuevas, por ejemplo, de “centos”:

[root@localhost ~]# docker search centos
 NAME DESCRIPTION STARS OFFICIAL AUTOMATED
 centos The official build of CentOS. 3254 [OK]
 jdeathe/centos-ssh CentOS-6 6.8 x86_64 / CentOS-7 7.3.1611 x8... 63 [OK]
 nimmis/java-centos This is docker images of CentOS 7 with dif... 25 [OK]
 consol/centos-xfce-vnc Centos container with "headless" VNC sessi... 24 [OK]
 gluster/gluster-centos Official GlusterFS Image [ CentOS-7 + Glu... 18 [OK]
 torusware/speedus-centos Always updated official CentOS docker imag... 8 [OK]
 egyptianbman/docker-centos-nginx-php A simple and highly configurable docker co... 6 [OK]
 nathonfowlie/centos-jre Latest CentOS image with the JRE pre-insta... 5 [OK]
 centos/mariadb55-centos7 4 [OK]
 centos/redis Redis built for CentOS 2 [OK]
 harisekhon/centos-scala Scala + CentOS (OpenJDK tags 2.10-jre7 - 2... 2 [OK]
 harisekhon/centos-java Java on CentOS (OpenJDK, tags jre/jdk7-8) 2 [OK]
 freenas/centos Simple CentOS Linux interactive container 1 [OK]
 blacklabelops/centos CentOS Base Image! Built and Updates Daily! 1 [OK]
 darksheer/centos Base Centos Image -- Updated hourly 1 [OK]
 sgfinans/docker-centos CentOS with a running sshd and Docker 1 [OK]
 timhughes/centos Centos with systemd installed and running 1 [OK]
 januswel/centos yum update-ed CentOS image 0 [OK]
 grossws/centos CentOS 6 and 7 base images with gosu and l... 0 [OK]
 grayzone/centos auto build for centos. 0 [OK]
 kz8s/centos Official CentOS plus epel-release 0 [OK]
 aguamala/centos CentOS base image 0 [OK]
 repositoryjp/centos Docker Image for CentOS. 0 [OK]
 vcatechnology/centos A CentOS Image which is updated daily 0 [OK]
 dmglab/centos CentOS with some extras - This is for the ... 0 [OK]

[root@localhost ~]# docker search centos

NAME DESCRIPTION STARS OFFICIAL AUTOMATED

centos The official build of CentOS. 3254 [OK]

jdeathe/centos-ssh CentOS-6 6.8 x86_64 / CentOS-7 7.3.1611 x8... 63 [OK]

nimmis/java-centos This is docker images of CentOS 7 with dif... 25 [OK]

consol/centos-xfce-vnc Centos container with "headless" VNC sessi... 24 [OK]

gluster/gluster-centos Official GlusterFS Image [ CentOS-7 + Glu... 18 [OK]

torusware/speedus-centos Always updated official CentOS docker imag... 8 [OK]

egyptianbman/docker-centos-nginx-php A simple and highly configurable docker co... 6 [OK]

nathonfowlie/centos-jre Latest CentOS image with the JRE pre-insta... 5 [OK]

centos/mariadb55-centos7 4 [OK]

centos/redis Redis built for CentOS 2 [OK]

harisekhon/centos-scala Scala + CentOS (OpenJDK tags 2.10-jre7 - 2... 2 [OK]

harisekhon/centos-java Java on CentOS (OpenJDK, tags jre/jdk7-8) 2 [OK]

freenas/centos Simple CentOS Linux interactive container 1 [OK]

blacklabelops/centos CentOS Base Image! Built and Updates Daily! 1 [OK]

darksheer/centos Base Centos Image -- Updated hourly 1 [OK]

sgfinans/docker-centos CentOS with a running sshd and Docker 1 [OK]

timhughes/centos Centos with systemd installed and running 1 [OK]

januswel/centos yum update-ed CentOS image 0 [OK]

grossws/centos CentOS 6 and 7 base images with gosu and l... 0 [OK]

grayzone/centos auto build for centos. 0 [OK]

kz8s/centos Official CentOS plus epel-release 0 [OK]

aguamala/centos CentOS base image 0 [OK]

repositoryjp/centos Docker Image for CentOS. 0 [OK]

vcatechnology/centos A CentOS Image which is updated daily 0 [OK]

dmglab/centos CentOS with some extras - This is for the ... 0 [OK]

Instalamos una oficial como es centos:

[root@localhost ~]# docker pull centos
Using default tag: latest
latest: Pulling from library/centos
93857f76ae30: Pull complete
Digest: sha256:4eda692c08e0a065ae91d74e82fff4af3da307b4341ad61fa61771cc4659af60
Status: Downloaded newer image for centos:latest

[root@localhost ~]# docker pull centos

Using default tag: latest

latest: Pulling from library/centos

93857f76ae30: Pull complete

Digest: sha256:4eda692c08e0a065ae91d74e82fff4af3da307b4341ad61fa61771cc4659af60

Status: Downloaded newer image for centos:latest

Arrancamos la imagen descargada:

[root@localhost ~]# docker run centos

1	[root@localhost ~]# docker run centos

Podemos ver las que tenemos arrancadas de esta forma:

[root@localhost ~]# docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
centos              latest              a8493f5f50ff        4 days ago          192MB
hello-world         latest              48b5124b2768        2 months ago        1.84kB

[root@localhost ~]# docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

centos latest a8493f5f50ff 4 days ago 192MB

hello-world latest 48b5124b2768 2 months ago 1.84kB

Si queremos conectarnos al docker como lo haríamos como una máquina virtual lanzamos el siguiente comando. Os pongo un ejemplo tonto, como paso de mi host, al docker:

[root@localhost ~]# hostname
localhost.localdomain
[root@localhost ~]# docker run -it centos
[root@f97e6a803bbf /]# hostname
f97e6a803bbf

[root@localhost ~]# hostname

localhost.localdomain

[root@localhost ~]# docker run -it centos

[root@f97e6a803bbf /]# hostname

f97e6a803bbf

Ahora le instalamos algo, un ejemplo con mysql:

[root@f97e6a803bbf /]# yum -y install mysql

1	[root@f97e6a803bbf /]# yum -y install mysql

Una vez instalado, si queremos guardar los cambios deberemos “sellar” el docker para poder utilizarlo de “plantilla” para otros dockers. Así que salimos de él y guardamos de esta forma:

[root@f97e6a803bbf /]# exit
exit
[root@localhost ~]# docker commit -m "Centos+Mysql" -a "El Blog de Negu" f97e6a803bbf repositorio/centos-mysql
sha256:ba6b5228fc45b102f5b69127085c046de91161448b00e595d8af916859408cf8

[root@f97e6a803bbf /]# exit

exit

[root@localhost ~]# docker commit -m "Centos+Mysql" -a "El Blog de Negu" f97e6a803bbf repositorio/centos-mysql

sha256:ba6b5228fc45b102f5b69127085c046de91161448b00e595d8af916859408cf8

Ahora vemos una imagen nueva:

[root@localhost ~]# docker images
REPOSITORY                 TAG                 IMAGE ID            CREATED              SIZE
<strong>repositorio/centos-mysql </strong>  latest              ba6b5228fc45        About a minute ago   365MB
centos                     latest              a8493f5f50ff        4 days ago           192MB
hello-world                latest              48b5124b2768        2 months ago         1.84kB