Understanding and Using Containers

What is a Container

A container is a self-contained ready-to-run application
This is what makes it different from a virtual machine!
Containers have all on board that is required to start the application
To start a container, a container runtime is required
The container runtime is running on a host platform and establishes communication between the local host kernel and the container
So, all containers, no matter what they do, run on top
of the same local host kernel

Container Components

Images are read-only environments that contain the runtime environment, which includes the application and all libraries it requires
Containers are the isolated runtime environments where the application is running. By using namespaces the containers can be offered as a strictly isolated environment
Registries are used to store images. Docker Hub is a common registry, other registries exist (like quay.io) and private registries can be created also

Containers are Linux!

Containers are based on features offered by the Linux
operating system
Linux Kernel Namespaces provide strict isolation between system components at different levels
- network
- file
- users
- processes
- IPCs
Linux CGroups offer resource allocation and limitation

Container Runtimes

The container runtime allows for starting and running the container on top of the host OS
The container runtime is responsible for all parts of running the container which are not already a part of the running container program itself
Different container runtime solutions exist
- docker
- Ixc
- runc
- cri-o
- containerd
These runtimes are included in the different container solutions

The OCI

OCI is the Open Containers Initiative (https://opencontainers.org)
It standardizes the use of containers
- The image-spec defines how to package a container in a “filesystem bundle”
- The runtime-spec defines how to run that filesystem in a container
OCI standardization ensures compatibility between containers, no matter which environment they originally come from
The result is that for instance images made for Docker work without modifications in Red Hat Podman

Docker

Docker is important in the container landscape, but Docker is NOT the only way to run containers
When it started in 2013, Docker offered the following:
- Container image format
- Dockerfile, which is a method for building container images
- A way to manage container images
- A way to run containers
- A way to manage container instances
- A solution to share container images
Podman is the main alternative to Docker

Alternatives to Docker

With the launch of RHEL 8, Red Hat started offering Podman as an alternative to Docker
- Podman runs containers without the need of having a daemon directly on top of the cri-o container runtime
- Buildah is the related service that is used for managing container images
Other solutions for running containers also exist
- LXC is a Linux-native container runtime
- systemd-nspawn offers containers integrated in Systemd

Registries

Container registries are used to provide access to container images
Registries make distribution of containers easier: anyone can publish images on public registries
Docker Hub (hub.docker.com) is the biggest registry
Other registries exist as well, like quay.io
It’s also possible to create private registries

Accessing Registries

Access to registries is normally free
In some cases, additional authorization is required and you’ll need an account to access registry contents
On Docker Hub, an account gives access to additional features
- Higher image pull limit
- Web hooks connecting to GitHub
Use the browser-based login, or docker login from the command line

Starting Containers

Many environments are available, let’s look at Docker
To use containers on RHEL 8 and related distributions, you can use podman instead of docker
Use dnf install -y container-tools to install podman and related utilities

Installing Docker on Ubuntu

sudo apt-get update
sudo apt-get install apt-transport-https ca-certificates curl gnupg-agent software-properties-common
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
sudo apt-key fingerprint OEBFCD88
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(Isb_release -cs) stable"
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io
sudo docker run hello-world

Running a Container

mkdir -p /var/www/html
echo hello from docker >> /var/www/html/index.html
docker run -d -p 8080:80 --name="myapache" -v /var/www/html:/var/www/html httpd
docker ps
ss -tunap | grep 8080
curl http://localhost:8080

[root@controller /]# mkdir -p /var/www/html

[root@controller /]# echo hello from docker >> /var/www/html/index.html

[root@controller /]# cat /var/www/html/index.html
hello from docker

[root@controller /]# docker run -d -p 8080:80 --name="myapache" -v /var/www/html:/var/www/html httpd
Unable to find image 'httpd:latest' locally
latest: Pulling from library/httpd
e1caac4eb9d2: Pull complete
87b0fe460fd9: Pull complete
4f4fb700ef54: Pull complete
9cebd3e3b523: Pull complete
e9304da947c5: Pull complete
b60d4b66b268: Pull complete
Digest: sha256:104f07de17ee186c8f37b9f561e04fbfe4cf080d78c6e5f3802fd08fd118c3da
Status: Downloaded newer image for httpd:latest
132a8601bc20a2fa997a19438087c412c049f6ea39dfbe7e7591aeb19f50269a

[root@controller /]# docker ps
CONTAINER ID   IMAGE     COMMAND              CREATED          STATUS          PORTS                                   NAMES
132a8601bc20   httpd     "httpd-foreground"   37 seconds ago   Up 34 seconds   0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapache

[root@controller /]# ss -tunap | grep 8080
tcp   LISTEN    0      2048                0.0.0.0:8080                 0.0.0.0:*     users:(("docker-proxy",pid=346482,fd=4))         
tcp   LISTEN    0      2048                   [::]:8080                    [::]:*     users:(("docker-proxy",pid=346490,fd=4))         

[root@controller /]# curl http://localhost:8080
<html><body><h1>It works!</h1></body></html>

[root@controller /]# mkdir -p /var/www/html

[root@controller /]# echo hello from docker >> /var/www/html/index.html

[root@controller /]# cat /var/www/html/index.html

hello from docker

[root@controller /]# docker run -d -p 8080:80 --name="myapache" -v /var/www/html:/var/www/html httpd

Unable to find image 'httpd:latest' locally

latest: Pulling from library/httpd

e1caac4eb9d2: Pull complete

87b0fe460fd9: Pull complete

4f4fb700ef54: Pull complete

9cebd3e3b523: Pull complete

e9304da947c5: Pull complete

b60d4b66b268: Pull complete

Digest: sha256:104f07de17ee186c8f37b9f561e04fbfe4cf080d78c6e5f3802fd08fd118c3da

Status: Downloaded newer image for httpd:latest

132a8601bc20a2fa997a19438087c412c049f6ea39dfbe7e7591aeb19f50269a

[root@controller /]# docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

132a8601bc20 httpd "httpd-foreground" 37 seconds ago Up 34 seconds 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapache

[root@controller /]# ss -tunap | grep 8080

tcp LISTEN 0 2048 0.0.0.0:8080 0.0.0.0:* users:(("docker-proxy",pid=346482,fd=4))

tcp LISTEN 0 2048 [::]:8080 [::]:* users:(("docker-proxy",pid=346490,fd=4))

[root@controller /]# curl http://localhost:8080

<html><body><h1>It works!</h1></body></html>

Running Another Container

docker run -it busybox will start the busybox container with an interactive terminal to the entrypoint application
Ctrl-p, Ctrl-q to disconnect and keep it running
exit to stop the current container application
- If you were connected to the entrypoint application, the container will stop
- If you were connected to another shell session, the container will continue

[root@controller /]# docker run -it busybox
Unable to find image 'busybox:latest' locally
latest: Pulling from library/busybox
9ad63333ebc9: Pull complete
Digest: sha256:6d9ac9237a84afe1516540f40a0fafdc86859b2141954b4d643af7066d598b74
Status: Downloaded newer image for busybox:latest
/ # ps
PID   USER     TIME  COMMAND
    1 root      0:00 sh
    7 root      0:00 ps
/ # ps aux
PID   USER     TIME  COMMAND
    1 root      0:00 sh
    8 root      0:00 ps aux
/ # exit
[root@controller /]# docker ps
CONTAINER ID   IMAGE     COMMAND              CREATED          STATUS          PORTS                                   NAMES
132a8601bc20   httpd     "httpd-foreground"   11 minutes ago   Up 11 minutes   0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapache

[root@controller /]# docker ps -a
CONTAINER ID   IMAGE         COMMAND              CREATED              STATUS                         PORTS                                   NAMES
9107d90d8447   busybox       "sh"                 About a minute ago   Exited (0) 10 seconds ago                                              youthful_chandrasekhar
132a8601bc20   httpd         "httpd-foreground"   11 minutes ago       Up 11 minutes                  0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapache
605cd349b37c   hello-world   "/hello"             About an hour ago    Exited (0) About an hour ago                                           nervous_keldysh
0d6983933a50   hello-world   "/hello"             12 hours ago         Exited (0) 12 hours ago                                                serene_curie

[root@controller /]# docker run -it busybox
/ # <ctrl+p><ctrl+q>

[root@controller /]# docker ps
CONTAINER ID   IMAGE     COMMAND              CREATED          STATUS          PORTS                                   NAMES
a96d522c5b20   busybox   "sh"                 45 seconds ago   Up 44 seconds                                           cool_pasteur
132a8601bc20   httpd     "httpd-foreground"   12 minutes ago   Up 12 minutes   0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapache

[root@controller /]# docker exec -it myapache sh

# ps aux
sh: 1: ps: not found

# ls /proc
1   acpi       cpuinfo    execdomains  ioports    kmsg         mdstat   net           self      sysrq-trigger  version
10  buddyinfo  crypto     fb           irq        kpagecgroup  meminfo  pagetypeinfo  slabinfo  sysvipc        vmallocinfo
8   bus        devices    filesystems  kallsyms   kpagecount   misc     partitions    softirqs  thread-self    vmstat
9   cgroups    diskstats  fs           kcore      kpageflags   modules  sched_debug   stat      timer_list     xen
92  cmdline    dma        interrupts   key-users  loadavg      mounts   schedstat     swaps     tty            zoneinfo
98  consoles   driver     iomem        keys       locks        mtrr     scsi          sys       uptime

# cat /proc/1/cmdline
httpd-DFOREGROUND
# exit

[root@controller /]# docker ps
CONTAINER ID   IMAGE     COMMAND              CREATED          STATUS          PORTS                                   NAMES
a96d522c5b20   busybox   "sh"                 3 minutes ago    Up 3 minutes                                            cool_pasteur
132a8601bc20   httpd     "httpd-foreground"   15 minutes ago   Up 15 minutes   0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapache

[root@controller /]# docker run -it busybox

Unable to find image 'busybox:latest' locally

latest: Pulling from library/busybox

9ad63333ebc9: Pull complete

Digest: sha256:6d9ac9237a84afe1516540f40a0fafdc86859b2141954b4d643af7066d598b74

Status: Downloaded newer image for busybox:latest

/ # ps

PID USER TIME COMMAND

1 root 0:00 sh

7 root 0:00 ps

/ # ps aux

PID USER TIME COMMAND

1 root 0:00 sh

8 root 0:00 ps aux

/ # exit

[root@controller /]# docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

132a8601bc20 httpd "httpd-foreground" 11 minutes ago Up 11 minutes 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapache

[root@controller /]# docker ps -a

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

9107d90d8447 busybox "sh" About a minute ago Exited (0) 10 seconds ago youthful_chandrasekhar

132a8601bc20 httpd "httpd-foreground" 11 minutes ago Up 11 minutes 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapache

605cd349b37c hello-world "/hello" About an hour ago Exited (0) About an hour ago nervous_keldysh

0d6983933a50 hello-world "/hello" 12 hours ago Exited (0) 12 hours ago serene_curie

[root@controller /]# docker run -it busybox

/ # <ctrl+p><ctrl+q>

[root@controller /]# docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

a96d522c5b20 busybox "sh" 45 seconds ago Up 44 seconds cool_pasteur

132a8601bc20 httpd "httpd-foreground" 12 minutes ago Up 12 minutes 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapache

[root@controller /]# docker exec -it myapache sh

# ps aux

sh: 1: ps: not found

# ls /proc

1 acpi cpuinfo execdomains ioports kmsg mdstat net self sysrq-trigger version

10 buddyinfo crypto fb irq kpagecgroup meminfo pagetypeinfo slabinfo sysvipc vmallocinfo

8 bus devices filesystems kallsyms kpagecount misc partitions softirqs thread-self vmstat

9 cgroups diskstats fs kcore kpageflags modules sched_debug stat timer_list xen

92 cmdline dma interrupts key-users loadavg mounts schedstat swaps tty zoneinfo

98 consoles driver iomem keys locks mtrr scsi sys uptime

# cat /proc/1/cmdline

httpd-DFOREGROUND

# exit

[root@controller /]# docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

a96d522c5b20 busybox "sh" 3 minutes ago Up 3 minutes cool_pasteur

132a8601bc20 httpd "httpd-foreground" 15 minutes ago Up 15 minutes 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapache

Managing Containers – Common Commands

docker ps [-a]: shows currently [and past] running containers
docker start: starts a container from a locally stored image
docker stop: stops a container using Linux SIGTERM
docker restart: restarts a currently running container
docker kill: stops a container using Linux SIGKILL
docker rm: removes all container files from the host operating system

Inspecting Container Settings

docker ps will show the IDs of containers: pick one!
docker inspect <ID> | less
docker inspect --format='{{.NetworkSettings.IPAddress}}' containername
docker inspect --format ='{{.State.Pid}}' containername
Alternatively, use ps aux on the host to find the container PID

[root@controller /]# docker ps -a
CONTAINER ID   IMAGE         COMMAND              CREATED          STATUS                      PORTS                                   NAMES
a96d522c5b20   busybox       "sh"                 33 minutes ago   Up 33 minutes                                                       cool_pasteur
9107d90d8447   busybox       "sh"                 35 minutes ago   Exited (0) 34 minutes ago                                           youthful_chandrasekhar
132a8601bc20   httpd         "httpd-foreground"   45 minutes ago   Up 45 minutes               0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapache
605cd349b37c   hello-world   "/hello"             2 hours ago      Exited (0) 2 hours ago                                              nervous_keldysh
0d6983933a50   hello-world   "/hello"             13 hours ago     Exited (0) 13 hours ago                                             serene_curie

[root@controller /]# docker inspect youthful_chandrasekhar | more
[
    {
        "Id": "9107d90d8447d0f70238eb121660e4db746048d37d3294dd3ec0e8215006752b",
        "Created": "2024-02-20T10:02:35.922550351Z",
        "Path": "sh",
        "Args": [],
        "State": {
            "Status": "exited",
            "Running": false,
            "Paused": false,
            "Restarting": false,
            "OOMKilled": false,
            "Dead": false,
            "Pid": 0,
            "ExitCode": 0,
            "Error": "",
            "StartedAt": "2024-02-20T10:02:36.401131212Z",
            "FinishedAt": "2024-02-20T10:04:14.878553209Z"
        },
...
[root@controller /]# docker ps
CONTAINER ID   IMAGE     COMMAND              CREATED          STATUS          PORTS                                   NAMES
a96d522c5b20   busybox   "sh"                 33 minutes ago   Up 33 minutes                                           cool_pasteur
132a8601bc20   httpd     "httpd-foreground"   45 minutes ago   Up 45 minutes   0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapache

[root@controller /]# docker inspect cool_pasteur | more
[
    {
        "Id": "a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00",
        "Created": "2024-02-20T10:05:07.9709231Z",
        "Path": "sh",
        "Args": [],
        "State": {
            "Status": "running",
            "Running": true,
            "Paused": false,
            "Restarting": false,
            "OOMKilled": false,
            "Dead": false,
            "Pid": 349943,
            "ExitCode": 0,
            "Error": "",
            "StartedAt": "2024-02-20T10:05:08.410217942Z",
            "FinishedAt": "0001-01-01T00:00:00Z"
        },
        "Image": "sha256:3f57d9401f8d42f986df300f0c69192fc41da28ccc8d797829467780db3dd741",
        "ResolvConfPath": "/var/lib/docker/containers/a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00/resolv.conf",
        "HostnamePath": "/var/lib/docker/containers/a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00/hostname",
        "HostsPath": "/var/lib/docker/containers/a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00/hosts",
        "LogPath": "/var/lib/docker/containers/a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00/a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00-json.l
og",
...
[root@controller /]# docker inspect --format='{{.NetworkSettings.IPAddress}}' cool_pasteur
172.17.0.3

[root@controller /]# docker inspect --format ='{{.State.Pid}}' cool_pasteur
=349943

[root@controller /]# ps fax | more
    PID TTY      STAT   TIME COMMAND
      2 ?        S      0:00 [kthreadd]
      3 ?        I<     0:00  \_ [rcu_gp]
      4 ?        I<     0:00  \_ [rcu_par_gp]
      5 ?        I<     0:00  \_ [slub_flushwq]
      7 ?        I<     0:00  \_ [kworker/0:0H-events_highpri]
     10 ?        I<     0:00  \_ [mm_percpu_wq]
     11 ?        S      0:00  \_ [rcu_tasks_rude_]
     12 ?        S      0:00  \_ [rcu_tasks_trace]
     13 ?        S      0:00  \_ [ksoftirqd/0]
     14 ?        I      0:51  \_ [rcu_sched]

[root@controller /]# docker ps -a

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

a96d522c5b20 busybox "sh" 33 minutes ago Up 33 minutes cool_pasteur

9107d90d8447 busybox "sh" 35 minutes ago Exited (0) 34 minutes ago youthful_chandrasekhar

132a8601bc20 httpd "httpd-foreground" 45 minutes ago Up 45 minutes 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapache

605cd349b37c hello-world "/hello" 2 hours ago Exited (0) 2 hours ago nervous_keldysh

0d6983933a50 hello-world "/hello" 13 hours ago Exited (0) 13 hours ago serene_curie

[root@controller /]# docker inspect youthful_chandrasekhar | more

[

{

"Id": "9107d90d8447d0f70238eb121660e4db746048d37d3294dd3ec0e8215006752b",

"Created": "2024-02-20T10:02:35.922550351Z",

"Path": "sh",

"Args": [],

"State": {

"Status": "exited",

"Running": false,

"Paused": false,

"Restarting": false,

"OOMKilled": false,

"Dead": false,

"Pid": 0,

"ExitCode": 0,

"Error": "",

"StartedAt": "2024-02-20T10:02:36.401131212Z",

"FinishedAt": "2024-02-20T10:04:14.878553209Z"

...

[root@controller /]# docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

a96d522c5b20 busybox "sh" 33 minutes ago Up 33 minutes cool_pasteur

132a8601bc20 httpd "httpd-foreground" 45 minutes ago Up 45 minutes 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapache

[root@controller /]# docker inspect cool_pasteur | more

[

{

"Id": "a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00",

"Created": "2024-02-20T10:05:07.9709231Z",

"Path": "sh",

"Args": [],

"State": {

"Status": "running",

"Running": true,

"Paused": false,

"Restarting": false,

"OOMKilled": false,

"Dead": false,

"Pid": 349943,

"ExitCode": 0,

"Error": "",

"StartedAt": "2024-02-20T10:05:08.410217942Z",

"FinishedAt": "0001-01-01T00:00:00Z"

"Image": "sha256:3f57d9401f8d42f986df300f0c69192fc41da28ccc8d797829467780db3dd741",

"ResolvConfPath": "/var/lib/docker/containers/a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00/resolv.conf",

"HostnamePath": "/var/lib/docker/containers/a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00/hostname",

"HostsPath": "/var/lib/docker/containers/a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00/hosts",

"LogPath": "/var/lib/docker/containers/a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00/a96d522c5b2095c33aa647f52807727831b161815937f0500941e685f22f8a00-json.l

og",

...

[root@controller /]# docker inspect --format='{{.NetworkSettings.IPAddress}}' cool_pasteur

172.17.0.3

[root@controller /]# docker inspect --format ='{{.State.Pid}}' cool_pasteur

=349943

[root@controller /]# ps fax | more

PID TTY STAT TIME COMMAND

2 ? S 0:00 [kthreadd]

3 ? I< 0:00 \_ [rcu_gp]

4 ? I< 0:00 \_ [rcu_par_gp]

5 ? I< 0:00 \_ [slub_flushwq]

7 ? I< 0:00 \_ [kworker/0:0H-events_highpri]

10 ? I< 0:00 \_ [mm_percpu_wq]

11 ? S 0:00 \_ [rcu_tasks_rude_]

12 ? S 0:00 \_ [rcu_tasks_trace]

13 ? S 0:00 \_ [ksoftirqd/0]

14 ? I 0:51 \_ [rcu_sched]

Managing Images

After fetching, the container images are stored on the host
Use docker images to get a list of images
Or use docker image --help to get an overview of all options related to managing container images

[root@controller /]# docker images
REPOSITORY    TAG       IMAGE ID       CREATED        SIZE
busybox       latest    3f57d9401f8d   4 weeks ago    4.26MB
httpd         latest    2776f4da9d55   4 weeks ago    167MB
hello-world   latest    d2c94e258dcb   9 months ago   13.3kB
[root@controller /]# docker image
Usage:  docker image COMMAND
Manage images
Commands:
  build       Build an image from a Dockerfile
  history     Show the history of an image
  import      Import the contents from a tarball to create a filesystem image
  inspect     Display detailed information on one or more images
  load        Load an image from a tar archive or STDIN
  ls          List images
  prune       Remove unused images
  pull        Download an image from a registry
  push        Upload an image to a registry
  rm          Remove one or more images
  save        Save one or more images to a tar archive (streamed to STDOUT by default)
  tag         Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE

[root@controller /]# docker image ls
REPOSITORY    TAG       IMAGE ID       CREATED        SIZE
busybox       latest    3f57d9401f8d   4 weeks ago    4.26MB
httpd         latest    2776f4da9d55   4 weeks ago    167MB
hello-world   latest    d2c94e258dcb   9 months ago   13.3kB

[root@controller /]# docker image inspect 3f57d9401f8d | more
[
    {
        "Id": "sha256:3f57d9401f8d42f986df300f0c69192fc41da28ccc8d797829467780db3dd741",
        "RepoTags": [
            "busybox:latest"
        ],
        "RepoDigests": [
            "busybox@sha256:6d9ac9237a84afe1516540f40a0fafdc86859b2141954b4d643af7066d598b74"
        ],
        "Parent": "",
        "Comment": "buildkit.dockerfile.v0",
        "Created": "2024-01-17T21:49:12Z",
        "Container": "",
        "ContainerConfig": {
            "Hostname": "",
            "Domainname": "",
...
[root@controller /]# docker image ls
REPOSITORY    TAG       IMAGE ID       CREATED        SIZE
busybox       latest    3f57d9401f8d   4 weeks ago    4.26MB
httpd         latest    2776f4da9d55   4 weeks ago    167MB
hello-world   latest    d2c94e258dcb   9 months ago   13.3kB

[root@controller /]# docker image rm d2c94e258dcb
Error response from daemon: conflict: unable to delete d2c94e258dcb (must be forced) - image is being used by stopped container 0d6983933a50

[root@controller /]# docker image rm -f d2c94e258dcb
Untagged: hello-world:latest
Untagged: hello-world@sha256:d000bc569937abbe195e20322a0bde6b2922d805332fd6d8a68b19f524b7d21d
Deleted: sha256:d2c94e258dcb3c5ac2798d32e1249e42ef01cba4841c2234249495f87264ac5a

[root@controller /]# docker images

REPOSITORY TAG IMAGE ID CREATED SIZE

busybox latest 3f57d9401f8d 4 weeks ago 4.26MB

httpd latest 2776f4da9d55 4 weeks ago 167MB

hello-world latest d2c94e258dcb 9 months ago 13.3kB

[root@controller /]# docker image

Usage: docker image COMMAND

Manage images

Commands:

build Build an image from a Dockerfile

history Show the history of an image

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

inspect Display detailed information on one or more images

load Load an image from a tar archive or STDIN

ls List images

prune Remove unused images

pull Download an image from a registry

push Upload an image to a registry

rm Remove one or more images

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

tag Create a tag TARGET_IMAGE that refers to SOURCE_IMAGE

[root@controller /]# docker image ls

REPOSITORY TAG IMAGE ID CREATED SIZE

busybox latest 3f57d9401f8d 4 weeks ago 4.26MB

httpd latest 2776f4da9d55 4 weeks ago 167MB

hello-world latest d2c94e258dcb 9 months ago 13.3kB

[root@controller /]# docker image inspect 3f57d9401f8d | more

[

{

"Id": "sha256:3f57d9401f8d42f986df300f0c69192fc41da28ccc8d797829467780db3dd741",

"RepoTags": [

"busybox:latest"

"RepoDigests": [

"busybox@sha256:6d9ac9237a84afe1516540f40a0fafdc86859b2141954b4d643af7066d598b74"

"Parent": "",

"Comment": "buildkit.dockerfile.v0",

"Created": "2024-01-17T21:49:12Z",

"Container": "",

"ContainerConfig": {

"Hostname": "",

"Domainname": "",

...

[root@controller /]# docker image ls

REPOSITORY TAG IMAGE ID CREATED SIZE

busybox latest 3f57d9401f8d 4 weeks ago 4.26MB

httpd latest 2776f4da9d55 4 weeks ago 167MB

hello-world latest d2c94e258dcb 9 months ago 13.3kB

[root@controller /]# docker image rm d2c94e258dcb

Error response from daemon: conflict: unable to delete d2c94e258dcb (must be forced) - image is being used by stopped container 0d6983933a50

[root@controller /]# docker image rm -f d2c94e258dcb

Untagged: hello-world:latest

Untagged: hello-world@sha256:d000bc569937abbe195e20322a0bde6b2922d805332fd6d8a68b19f524b7d21d

Deleted: sha256:d2c94e258dcb3c5ac2798d32e1249e42ef01cba4841c2234249495f87264ac5a

Container Logging

The container application does not connect to a STDOUT, which is why logs,
by default, are written to the container
Use docker logs mycontainer to get access to the container log
Using docker logs is convenient for troubleshooting

[root@controller /]# docker run mariadb
Unable to find image 'mariadb:latest' locally
latest: Pulling from library/mariadb
01007420e9b0: Pull complete
0afd642f34d1: Pull complete
696ca6335161: Pull complete
a7e0c48ca7d7: Pull complete
8d9e67098d76: Pull complete
72f5e793adab: Pull complete
d5f886ae8a97: Pull complete
7e77db7838e8: Pull complete
Digest: sha256:55d9608d84658cbc691f52cd6389386a15e6c671cb5708b9f3af5782af3b4dbb
Status: Downloaded newer image for mariadb:latest
2024-02-20 11:21:20+00:00 [Note] [Entrypoint]: Entrypoint script for MariaDB Server 1:11.2.3+maria~ubu2204 started.
2024-02-20 11:21:21+00:00 [Warn] [Entrypoint]: /sys/fs/cgroup/pids:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
11:cpu,cpuacct:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
10:rdma:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
9:blkio:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
8:memory:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
7:hugetlb:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
6:net_cls,net_prio:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
5:perf_event:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
4:freezer:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
3:devices:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
2:cpuset:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
1:name=systemd:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a
0:://memory.pressure not writable, functionality unavailable to MariaDB
2024-02-20 11:21:21+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'
2024-02-20 11:21:21+00:00 [Note] [Entrypoint]: Entrypoint script for MariaDB Server 1:11.2.3+maria~ubu2204 started.
2024-02-20 11:21:21+00:00 [ERROR] [Entrypoint]: Database is uninitialized and password option is not specified
        You need to specify one of MARIADB_ROOT_PASSWORD, MARIADB_ROOT_PASSWORD_HASH, MARIADB_ALLOW_EMPTY_ROOT_PASSWORD and MARIADB_RANDOM_ROOT_PASSWORD

[root@controller /]# docker run -d mariadb
3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

[root@controller /]# docker ps
CONTAINER ID   IMAGE     COMMAND              CREATED             STATUS             PORTS                                   NAMES
a96d522c5b20   busybox   "sh"                 About an hour ago   Up About an hour                                           cool_pasteur
132a8601bc20   httpd     "httpd-foreground"   About an hour ago   Up About an hour   0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapache

[root@controller /]# docker ps -a
CONTAINER ID   IMAGE          COMMAND                  CREATED             STATUS                         PORTS                                   NAMES
3429b13ec1e9   mariadb        "docker-entrypoint.s…"   17 seconds ago      Exited (1) 14 seconds ago                                              trusting_rosalind
e8628333ea49   mariadb        "docker-entrypoint.s…"   54 seconds ago      Exited (1) 48 seconds ago                                              sharp_kowalevski
a96d522c5b20   busybox        "sh"                     About an hour ago   Up About an hour                                                       cool_pasteur
9107d90d8447   busybox        "sh"                     About an hour ago   Exited (0) About an hour ago                                           youthful_chandrasekhar
132a8601bc20   httpd          "httpd-foreground"       About an hour ago   Up About an hour               0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapache
605cd349b37c   d2c94e258dcb   "/hello"                 3 hours ago         Exited (0) 3 hours ago                                                 nervous_keldysh
0d6983933a50   d2c94e258dcb   "/hello"                 14 hours ago        Exited (0) 14 hours ago                                                serene_curie

[root@controller /]# docker logs trusting_rosalind
2024-02-20 11:21:54+00:00 [Note] [Entrypoint]: Entrypoint script for MariaDB Server 1:11.2.3+maria~ubu2204 started.
2024-02-20 11:21:55+00:00 [Warn] [Entrypoint]: /sys/fs/cgroup/pids:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
11:cpu,cpuacct:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
10:rdma:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
9:blkio:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
8:memory:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
7:hugetlb:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
6:net_cls,net_prio:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
5:perf_event:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
4:freezer:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
3:devices:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
2:cpuset:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
1:name=systemd:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f
0:://memory.pressure not writable, functionality unavailable to MariaDB
2024-02-20 11:21:55+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'
2024-02-20 11:21:55+00:00 [Note] [Entrypoint]: Entrypoint script for MariaDB Server 1:11.2.3+maria~ubu2204 started.
2024-02-20 11:21:55+00:00 [ERROR] [Entrypoint]: Database is uninitialized and password option is not specified
        You need to specify one of MARIADB_ROOT_PASSWORD, MARIADB_ROOT_PASSWORD_HASH, MARIADB_ALLOW_EMPTY_ROOT_PASSWORD and MARIADB_RANDOM_ROOT_PASSWORD

[root@controller /]# docker run -d --name mydb mariadb -e MYSQL_ROOT_PASSWORD=password
2024-02-20 11:25:50+00:00 [Note] [Entrypoint]: Entrypoint script for MariaDB Server 1:11.2.3+maria~ubu2204 started.
2024-02-20 11:25:50+00:00 [ERROR] [Entrypoint]: mariadbd failed while attempting to check config
        command was: mariadbd -e MYSQL_ROOT_PASSWORD=password --verbose --help
        2024-02-20 11:25:50 0 [Warning] Could not open mysql.plugin table: "Table 'mysql.plugin' doesn't exist". Some options may be missing from the help text
2024-02-20 11:25:50 0 [ERROR] mariadbd: unknown option '-e'

[root@controller /]# docker run -d --name mydb -e MYSQL_ROOT_PASSWORD=password mariadb
docker: Error response from daemon: Conflict. The container name "/mydb" is already in use by container "25dfb9b7e1104550fc60ac7f556fb654637ef3457c3be31ae7c148ccb3c4239a". You have to remove (or rename) that container to be able to reuse that name.
See 'docker run --help'.

[root@controller /]# docker rm mydb
mydb
[root@controller /]# docker run -d --name mydb -e MYSQL_ROOT_PASSWORD=password mariadb
a229ccfd0f818f06b641ca38350e49cb7528732915166c0baeaec16d204cb9bf

[root@controller /]# docker ps
CONTAINER ID   IMAGE     COMMAND                  CREATED             STATUS             PORTS                                   NAMES
a229ccfd0f81   mariadb   "docker-entrypoint.s…"   33 seconds ago      Up 31 seconds      3306/tcp                                mydb
a96d522c5b20   busybox   "sh"                     About an hour ago   Up About an hour                                           cool_pasteur
132a8601bc20   httpd     "httpd-foreground"       2 hours ago         Up 2 hours         0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapache

[root@controller /]# docker run mariadb

Unable to find image 'mariadb:latest' locally

latest: Pulling from library/mariadb

01007420e9b0: Pull complete

0afd642f34d1: Pull complete

696ca6335161: Pull complete

a7e0c48ca7d7: Pull complete

8d9e67098d76: Pull complete

72f5e793adab: Pull complete

d5f886ae8a97: Pull complete

7e77db7838e8: Pull complete

Digest: sha256:55d9608d84658cbc691f52cd6389386a15e6c671cb5708b9f3af5782af3b4dbb

Status: Downloaded newer image for mariadb:latest

2024-02-20 11:21:20+00:00 [Note] [Entrypoint]: Entrypoint script for MariaDB Server 1:11.2.3+maria~ubu2204 started.

2024-02-20 11:21:21+00:00 [Warn] [Entrypoint]: /sys/fs/cgroup/pids:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

11:cpu,cpuacct:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

10:rdma:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

9:blkio:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

8:memory:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

7:hugetlb:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

6:net_cls,net_prio:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

5:perf_event:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

4:freezer:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

3:devices:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

2:cpuset:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

1:name=systemd:/docker/e8628333ea4940fdcf8352e04b7106be21d9c65c023013f05d52f46ee5b5378a

0:://memory.pressure not writable, functionality unavailable to MariaDB

2024-02-20 11:21:21+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'

2024-02-20 11:21:21+00:00 [Note] [Entrypoint]: Entrypoint script for MariaDB Server 1:11.2.3+maria~ubu2204 started.

2024-02-20 11:21:21+00:00 [ERROR] [Entrypoint]: Database is uninitialized and password option is not specified

You need to specify one of MARIADB_ROOT_PASSWORD, MARIADB_ROOT_PASSWORD_HASH, MARIADB_ALLOW_EMPTY_ROOT_PASSWORD and MARIADB_RANDOM_ROOT_PASSWORD

[root@controller /]# docker run -d mariadb

3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

[root@controller /]# docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

a96d522c5b20 busybox "sh" About an hour ago Up About an hour cool_pasteur

132a8601bc20 httpd "httpd-foreground" About an hour ago Up About an hour 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapache

[root@controller /]# docker ps -a

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

3429b13ec1e9 mariadb "docker-entrypoint.s…" 17 seconds ago Exited (1) 14 seconds ago trusting_rosalind

e8628333ea49 mariadb "docker-entrypoint.s…" 54 seconds ago Exited (1) 48 seconds ago sharp_kowalevski

a96d522c5b20 busybox "sh" About an hour ago Up About an hour cool_pasteur

9107d90d8447 busybox "sh" About an hour ago Exited (0) About an hour ago youthful_chandrasekhar

132a8601bc20 httpd "httpd-foreground" About an hour ago Up About an hour 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapache

605cd349b37c d2c94e258dcb "/hello" 3 hours ago Exited (0) 3 hours ago nervous_keldysh

0d6983933a50 d2c94e258dcb "/hello" 14 hours ago Exited (0) 14 hours ago serene_curie

[root@controller /]# docker logs trusting_rosalind

2024-02-20 11:21:54+00:00 [Note] [Entrypoint]: Entrypoint script for MariaDB Server 1:11.2.3+maria~ubu2204 started.

2024-02-20 11:21:55+00:00 [Warn] [Entrypoint]: /sys/fs/cgroup/pids:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

11:cpu,cpuacct:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

10:rdma:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

9:blkio:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

8:memory:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

7:hugetlb:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

6:net_cls,net_prio:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

5:perf_event:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

4:freezer:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

3:devices:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

2:cpuset:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

1:name=systemd:/docker/3429b13ec1e95890be2f06714d1a688785be7154453c5f78ef0cca68e995098f

0:://memory.pressure not writable, functionality unavailable to MariaDB

2024-02-20 11:21:55+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'

2024-02-20 11:21:55+00:00 [Note] [Entrypoint]: Entrypoint script for MariaDB Server 1:11.2.3+maria~ubu2204 started.

2024-02-20 11:21:55+00:00 [ERROR] [Entrypoint]: Database is uninitialized and password option is not specified

You need to specify one of MARIADB_ROOT_PASSWORD, MARIADB_ROOT_PASSWORD_HASH, MARIADB_ALLOW_EMPTY_ROOT_PASSWORD and MARIADB_RANDOM_ROOT_PASSWORD

[root@controller /]# docker run -d --name mydb mariadb -e MYSQL_ROOT_PASSWORD=password

2024-02-20 11:25:50+00:00 [Note] [Entrypoint]: Entrypoint script for MariaDB Server 1:11.2.3+maria~ubu2204 started.

2024-02-20 11:25:50+00:00 [ERROR] [Entrypoint]: mariadbd failed while attempting to check config

command was: mariadbd -e MYSQL_ROOT_PASSWORD=password --verbose --help

2024-02-20 11:25:50 0 [Warning] Could not open mysql.plugin table: "Table 'mysql.plugin' doesn't exist". Some options may be missing from the help text

2024-02-20 11:25:50 0 [ERROR] mariadbd: unknown option '-e'

[root@controller /]# docker run -d --name mydb -e MYSQL_ROOT_PASSWORD=password mariadb

docker: Error response from daemon: Conflict. The container name "/mydb" is already in use by container "25dfb9b7e1104550fc60ac7f556fb654637ef3457c3be31ae7c148ccb3c4239a". You have to remove (or rename) that container to be able to reuse that name.

See 'docker run --help'.

[root@controller /]# docker rm mydb

mydb

[root@controller /]# docker run -d --name mydb -e MYSQL_ROOT_PASSWORD=password mariadb

a229ccfd0f818f06b641ca38350e49cb7528732915166c0baeaec16d204cb9bf

[root@controller /]# docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

a229ccfd0f81 mariadb "docker-entrypoint.s…" 33 seconds ago Up 31 seconds 3306/tcp mydb

a96d522c5b20 busybox "sh" About an hour ago Up About an hour cool_pasteur

132a8601bc20 httpd "httpd-foreground" 2 hours ago Up 2 hours 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapache

Lab: Using Containers

Run the latest version of Ubuntu in a container
In interactive mode, start a bash shell and explore the /etc/os-release file, as well as the kernel version (uname -r)
Disconnect from the container without shutting it down

[root@controller /]# docker run -it ubuntu:latest
Unable to find image 'ubuntu:latest' locally
latest: Pulling from library/ubuntu
01007420e9b0: Already exists
Digest: sha256:f9d633ff6640178c2d0525017174a688e2c1aef28f0a0130b26bd5554491f0da
Status: Downloaded newer image for ubuntu:latest

root@cc94dcd26493:/# cat /etc/os-release
PRETTY_NAME="Ubuntu 22.04.3 LTS"
NAME="Ubuntu"
VERSION_ID="22.04"
VERSION="22.04.3 LTS (Jammy Jellyfish)"
VERSION_CODENAME=jammy
ID=ubuntu
ID_LIKE=debian
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
UBUNTU_CODENAME=jammy

root@cc94dcd26493:/# uname -r
4.18.0-500.el8.x86_64

root@cc94dcd26493:/# <ctrl+p><ctrl+q>
[root@controller /]#

[root@controller /]# uname -r
4.18.0-500.el8.x86_64

[root@controller /]# docker ps
CONTAINER ID   IMAGE           COMMAND                  CREATED              STATUS              PORTS                                   NAMES
cc94dcd26493   ubuntu:latest   "/bin/bash"              About a minute ago   Up About a minute                                           sweet_mclean
a229ccfd0f81   mariadb         "docker-entrypoint.s…"   6 minutes ago        Up 6 minutes        3306/tcp                                mydb
a96d522c5b20   busybox         "sh"                     2 hours ago          Up 2 hours                                                  cool_pasteur
132a8601bc20   httpd           "httpd-foreground"       2 hours ago          Up 2 hours          0.0.0.0:8080->80/tcp, :::8080->80/tcp   myapac

[root@controller /]# docker run -it ubuntu:latest

Unable to find image 'ubuntu:latest' locally

latest: Pulling from library/ubuntu

01007420e9b0: Already exists

Digest: sha256:f9d633ff6640178c2d0525017174a688e2c1aef28f0a0130b26bd5554491f0da

Status: Downloaded newer image for ubuntu:latest

root@cc94dcd26493:/# cat /etc/os-release

PRETTY_NAME="Ubuntu 22.04.3 LTS"

NAME="Ubuntu"

VERSION_ID="22.04"

VERSION="22.04.3 LTS (Jammy Jellyfish)"

VERSION_CODENAME=jammy

ID=ubuntu

ID_LIKE=debian

HOME_URL="https://www.ubuntu.com/"

SUPPORT_URL="https://help.ubuntu.com/"

BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"

PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"

UBUNTU_CODENAME=jammy

root@cc94dcd26493:/# uname -r

4.18.0-500.el8.x86_64

root@cc94dcd26493:/# <ctrl+p><ctrl+q>

[root@controller /]#

[root@controller /]# uname -r

4.18.0-500.el8.x86_64

[root@controller /]# docker ps

CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES

cc94dcd26493 ubuntu:latest "/bin/bash" About a minute ago Up About a minute sweet_mclean

a229ccfd0f81 mariadb "docker-entrypoint.s…" 6 minutes ago Up 6 minutes 3306/tcp mydb

a96d522c5b20 busybox "sh" 2 hours ago Up 2 hours cool_pasteur

132a8601bc20 httpd "httpd-foreground" 2 hours ago Up 2 hours 0.0.0.0:8080->80/tcp, :::8080->80/tcp myapac

As we see the kernel version in the container is alwys the same like in the virtual machine.