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Run a dockerized service

Run a basic http server in a docker container

Let's deploy a simple web server using nginx. First of all, let's search on Docker Hub for an already available image.

We can use the search command as follows:

docker search nginx

You will get something like the following output:

NAME                              DESCRIPTION                                     STARS     OFFICIAL
nginx                             Official build of Nginx.                        20157     [OK]
nginx/nginx-quic-qns              NGINX QUIC interop                              1
nginx/nginx-ingress               NGINX and  NGINX Plus Ingress Controllers fo…   94
nginx/nginx-ingress-operator      NGINX Ingress Operator for NGINX and NGINX P…   2
nginx/nginx-prometheus-exporter   NGINX Prometheus Exporter for NGINX and NGIN…   43
nginx/unit                        This repository is retired, use the Docker o…   63
nginx/unit-preview                Unit preview features                           0
bitnami/nginx                     Bitnami container image for NGINX               193
rapidfort/nginx                   RapidFort optimized, hardened image for NGINX   15
kasmweb/nginx                     An Nginx image based off nginx:alpine and in…   8
ubuntu/nginx                      Nginx, a high-performance reverse proxy & we…   116
chainguard/nginx                  Minimal Wolfi-based nginx HTTP, reverse prox…   2
dockette/nginx                    Nginx SSL / HSTS / HTTP2                        3
jitesoft/nginx                    Nginx on alpine linux                           0
docksal/nginx                     Nginx service image for Docksal                 0
gluufederation/nginx               A customized NGINX image containing a consu…   1
okteto/nginx                                                                      0
objectscale/nginx                                                                 0
intel/nginx                                                                       0
circleci/nginx                    This image is for internal use                  2
bitnamicharts/nginx                                                               0
vmware/nginx                                                                      2
rancher/nginx                                                                     2
linuxserver/nginx                 An Nginx container, brought to you by LinuxS…   217
redash/nginx                      Pre-configured nginx to proxy linked contain…   2

Tip

The docker search command returns the following image information:

  • Repository names
  • Image descriptions
  • Stars - these measure the popularity of an image
  • Official - an image managed by the upstream developer (e.g., the fedora image managed by the Fedora team)
  • Automated - an image built by the Docker Hub's Automated Build process

In alternative, you can make a similar search on the Docker Hub Web site:

Search nginx image

Let's download the official image using the docker image pull command:

docker image pull nginx

Using default tag: latest
latest: Pulling from library/nginx
e4fff0779e6d: Pull complete
2a0cb278fd9f: Pull complete
7045d6c32ae2: Pull complete
03de31afb035: Pull complete
0f17be8dcff2: Pull complete
14b7e5e8f394: Pull complete
23fa5a7b99a6: Pull complete
Digest: sha256:447a8665cc1dab95b1ca778e162215839ccbb9189104c79d7ec3a81e14577add
Status: Downloaded newer image for nginx:latest
docker.io/library/nginx:latest

In order to list the images downloaded on your host, you can use the command:

docker image ls
The output of this command provides useful information, including the size of the image:

REPOSITORY    TAG       IMAGE ID       CREATED         SIZE
nginx         latest    5ef79149e0ec   2 weeks ago     188MB
ubuntu        latest    edbfe74c41f8   4 weeks ago     78.1MB
hello-world   latest    d2c94e258dcb   16 months ago   13.3kB

Let's have a look at the image with the commands we have already seen in the previous section:

docker image inspect nginx

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[
    {
        "Id": "sha256:5ef79149e0ec84a7a9f9284c3f91aa3c20608f8391f5445eabe92ef07dbda03c",
        "RepoTags": [
            "nginx:latest"
        ],
        "RepoDigests": [
            "nginx@sha256:447a8665cc1dab95b1ca778e162215839ccbb9189104c79d7ec3a81e14577add"
        ],
        "Parent": "",
        "Comment": "buildkit.dockerfile.v0",
        "Created": "2024-08-14T21:31:12Z",
        "DockerVersion": "",
        "Author": "",
        "Config": {
            "Hostname": "",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "ExposedPorts": {
                "80/tcp": {}
            },
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "NGINX_VERSION=1.27.1",
                "NJS_VERSION=0.8.5",
                "NJS_RELEASE=1~bookworm",
                "PKG_RELEASE=1~bookworm",
                "DYNPKG_RELEASE=2~bookworm"
            ],
            "Cmd": [
                "nginx",
                "-g",
                "daemon off;"
            ],
            "ArgsEscaped": true,
            "Image": "",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": [
                "/docker-entrypoint.sh"
            ],
            "OnBuild": null,
            "Labels": {
                "maintainer": "NGINX Docker Maintainers <docker-maint@nginx.com>"
            },
            "StopSignal": "SIGQUIT"
        },
        "Architecture": "amd64",
        "Os": "linux",
        "Size": 187694648,
        "GraphDriver": {
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/29bfd1646b549c5a2e7488cd2df0cfbf5b31e6e452390a6419590f798a5be2b7/diff:/var/lib/docker/overlay2/b9732ca651e6793c280fe0b6408bbebe59bbbebbdd596b40cfd51f469243892a/diff:/var/lib/docker/overlay2/2e84243b34f95d37bd725e031f33665c8a2ec89d99824bcb96a0694a52dcb7c9/diff:/var/lib/docker/overlay2/4d59513c75c18791768dc9a21232185999d0fa81c65506e950842b46565fb20b/diff:/var/lib/docker/overlay2/4bd3dd2794ec1e9f2729f9252882a1728abbd44a2e417feb55fbd019857d7054/diff:/var/lib/docker/overlay2/9145ec71e543c915530869f33be035a9f64642f304aa39acdd73b64d6d667d48/diff",
                "MergedDir": "/var/lib/docker/overlay2/670ced786458f0d0102c989a939e8808fdfd0e8c982c70d6173b7d7b36fe9e9d/merged",
                "UpperDir": "/var/lib/docker/overlay2/670ced786458f0d0102c989a939e8808fdfd0e8c982c70d6173b7d7b36fe9e9d/diff",
                "WorkDir": "/var/lib/docker/overlay2/670ced786458f0d0102c989a939e8808fdfd0e8c982c70d6173b7d7b36fe9e9d/work"
            },
            "Name": "overlay2"
        },
        "RootFS": {
            "Type": "layers",
            "Layers": [
                "sha256:9853575bc4f955c5892dd64187538a6cd02dba6968eba9201854876a7a257034",
                "sha256:72db5db515fdd9ae82b759fc207fdfbcc31567c28bb87950abc94ce1d60b2d40",
                "sha256:8b87c0c6652495401acfbe029ede84a5f327664770561ba5f8b7fe9149f52dd0",
                "sha256:ec1a2ca4ac8784def146544fc7068db06a188d2da4fd7c4e134a76415b8bc1a8",
                "sha256:55e54df86207fa772302a6fc1e78eb60bd7e3ebd4f913ef7f5ad668ad69ab64d",
                "sha256:f4f00eaedec7933a48b09f3948c685c41d55f0bf5906295dd022c05b65082344",
                "sha256:5f0272c6e96d5cd8ea1c6507cfce81980d4b99322bd037d99250a79d4c0b9f1a"
            ]
        },
        "Metadata": {
            "LastTagTime": "0001-01-01T00:00:00Z"
        }
    }
]

We can see that the nginx version in our container will be 1.27.1, the service will be listening on port 80 and the command that will be executed at the container start is nginx -g daemon off;.

This is a useful exercise, but in general you will find these information in the description of the image on Docker hub.

Creating a daemonized container

In addition to the interactive containers, we can create longer-running containers.

Daemonized containers don't have the interactive session we've used in our previous example and are ideal for running applications and services. Most of the containers you're likely to run will probably be daemonized.

Let's start a daemonized container now.

docker container run -d --name nginx nginx

Note

The -d flag tells Docker to detach the container to the background. The --name option allows to set a name for your container

Instead of being attached to a shell, the docker run command has instead returned a container ID and returned us to our command prompt.

We can see our container running with:

docker container ps

docker container ps
CONTAINER ID   IMAGE     COMMAND                  CREATED          STATUS          PORTS     NAMES
43147119c02a   nginx     "/docker-entrypoint.…"   20 seconds ago   Up 12 seconds   80/tcp    nginx

Getting the container log

What's happening inside our container? We can use the docker container logs command to fetch the log of a container:

docker container logs nginx

/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Sourcing /docker-entrypoint.d/15-local-resolvers.envsh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
2024/09/04 14:09:50 [notice] 1#1: using the "epoll" event method
2024/09/04 14:09:50 [notice] 1#1: nginx/1.27.1
2024/09/04 14:09:50 [notice] 1#1: built by gcc 12.2.0 (Debian 12.2.0-14)
2024/09/04 14:09:50 [notice] 1#1: OS: Linux 6.8.0-40-generic
2024/09/04 14:09:50 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 1048576:1048576
2024/09/04 14:09:50 [notice] 1#1: start worker processes
2024/09/04 14:09:50 [notice] 1#1: start worker process 29
2024/09/04 14:09:50 [notice] 1#1: start worker process 30

Tip

We can also monitor the container's logs much like the tail -f binary operates using the -f flag. You can also tail a portion of the logs of a container by using the --tail option. Moreover you can also use the -t flag to prefix the log entries with timestamps.

Inspecting the container processes

We can inspect the processes running inside our container using the docker container top command:

docker container top nginx
UID                 PID                 PPID                C                   STIME               TTY                 TIME                CMD
root                49252               49232               0                   14:09               ?                   00:00:00            nginx: master process nginx -g daemon off;
message+            49301               49252               0                   14:09               ?                   00:00:00            nginx: worker process
message+            49302               49252               0                   14:09               ?                   00:00:00            nginx: worker process

Finding out more about our container

Let's use again the command docker container inspect to get more information about our container:

docker container inspect nginx

[
    {
        "Id": "43147119c02a544cffcc2e99a2bd634b6fcec63406e4d9ac510821f5cf140e60",
        "Created": "2024-09-04T14:09:42.284257833Z",
        "Path": "/docker-entrypoint.sh",
        "Args": [
            "nginx",
            "-g",
            "daemon off;"
        ],
        "State": {
            "Status": "running",
            "Running": true,
            "Paused": false,
            "Restarting": false,
            "OOMKilled": false,
            "Dead": false,
            "Pid": 49252,
            "ExitCode": 0,
            "Error": "",
            "StartedAt": "2024-09-04T14:09:49.261329401Z",
            "FinishedAt": "0001-01-01T00:00:00Z"
        },
        "Image": "sha256:5ef79149e0ec84a7a9f9284c3f91aa3c20608f8391f5445eabe92ef07dbda03c",
        "ResolvConfPath": "/var/lib/docker/containers/43147119c02a544cffcc2e99a2bd634b6fcec63406e4d9ac510821f5cf140e60/resolv.conf",
        "HostnamePath": "/var/lib/docker/containers/43147119c02a544cffcc2e99a2bd634b6fcec63406e4d9ac510821f5cf140e60/hostname",
        "HostsPath": "/var/lib/docker/containers/43147119c02a544cffcc2e99a2bd634b6fcec63406e4d9ac510821f5cf140e60/hosts",
        "LogPath": "/var/lib/docker/containers/43147119c02a544cffcc2e99a2bd634b6fcec63406e4d9ac510821f5cf140e60/43147119c02a544cffcc2e99a2bd634b6fcec63406e4d9ac510821f5cf140e60-json.log",
        "Name": "/nginx",
        "RestartCount": 0,
        "Driver": "overlay2",
        "Platform": "linux",
        "MountLabel": "",
        "ProcessLabel": "",
        "AppArmorProfile": "docker-default",
        "ExecIDs": null,
        "HostConfig": {
            "Binds": null,
            "ContainerIDFile": "",
            "LogConfig": {
                "Type": "json-file",
                "Config": {}
            },
            "NetworkMode": "bridge",
            "PortBindings": {},
            "RestartPolicy": {
                "Name": "no",
                "MaximumRetryCount": 0
            },
            "AutoRemove": false,
            "VolumeDriver": "",
            "VolumesFrom": null,
            "ConsoleSize": [
                39,
                178
            ],
            "CapAdd": null,
            "CapDrop": null,
            "CgroupnsMode": "private",
            "Dns": [],
            "DnsOptions": [],
            "DnsSearch": [],
            "ExtraHosts": null,
            "GroupAdd": null,
            "IpcMode": "private",
            "Cgroup": "",
            "Links": null,
            "OomScoreAdj": 0,
            "PidMode": "",
            "Privileged": false,
            "PublishAllPorts": false,
            "ReadonlyRootfs": false,
            "SecurityOpt": null,
            "UTSMode": "",
            "UsernsMode": "",
            "ShmSize": 67108864,
            "Runtime": "runc",
            "Isolation": "",
            "CpuShares": 0,
            "Memory": 0,
            "NanoCpus": 0,
            "CgroupParent": "",
            "BlkioWeight": 0,
            "BlkioWeightDevice": [],
            "BlkioDeviceReadBps": [],
            "BlkioDeviceWriteBps": [],
            "BlkioDeviceReadIOps": [],
            "BlkioDeviceWriteIOps": [],
            "CpuPeriod": 0,
            "CpuQuota": 0,
            "CpuRealtimePeriod": 0,
            "CpuRealtimeRuntime": 0,
            "CpusetCpus": "",
            "CpusetMems": "",
            "Devices": [],
            "DeviceCgroupRules": null,
            "DeviceRequests": null,
            "MemoryReservation": 0,
            "MemorySwap": 0,
            "MemorySwappiness": null,
            "OomKillDisable": null,
            "PidsLimit": null,
            "Ulimits": [],
            "CpuCount": 0,
            "CpuPercent": 0,
            "IOMaximumIOps": 0,
            "IOMaximumBandwidth": 0,
            "MaskedPaths": [
                "/proc/asound",
                "/proc/acpi",
                "/proc/kcore",
                "/proc/keys",
                "/proc/latency_stats",
                "/proc/timer_list",
                "/proc/timer_stats",
                "/proc/sched_debug",
                "/proc/scsi",
                "/sys/firmware",
                "/sys/devices/virtual/powercap"
            ],
            "ReadonlyPaths": [
                "/proc/bus",
                "/proc/fs",
                "/proc/irq",
                "/proc/sys",
                "/proc/sysrq-trigger"
            ]
        },
        "GraphDriver": {
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/2439f7d82ca5c505d4b56fde68aa78ba7caf71b3ca2cf1598dddff528566a964-init/diff:/var/lib/docker/overlay2/670ced786458f0d0102c989a939e8808fdfd0e8c982c70d6173b7d7b36fe9e9d/diff:/var/lib/docker/overlay2/29bfd1646b549c5a2e7488cd2df0cfbf5b31e6e452390a6419590f798a5be2b7/diff:/var/lib/docker/overlay2/b9732ca651e6793c280fe0b6408bbebe59bbbebbdd596b40cfd51f469243892a/diff:/var/lib/docker/overlay2/2e84243b34f95d37bd725e031f33665c8a2ec89d99824bcb96a0694a52dcb7c9/diff:/var/lib/docker/overlay2/4d59513c75c18791768dc9a21232185999d0fa81c65506e950842b46565fb20b/diff:/var/lib/docker/overlay2/4bd3dd2794ec1e9f2729f9252882a1728abbd44a2e417feb55fbd019857d7054/diff:/var/lib/docker/overlay2/9145ec71e543c915530869f33be035a9f64642f304aa39acdd73b64d6d667d48/diff",
                "MergedDir": "/var/lib/docker/overlay2/2439f7d82ca5c505d4b56fde68aa78ba7caf71b3ca2cf1598dddff528566a964/merged",
                "UpperDir": "/var/lib/docker/overlay2/2439f7d82ca5c505d4b56fde68aa78ba7caf71b3ca2cf1598dddff528566a964/diff",
                "WorkDir": "/var/lib/docker/overlay2/2439f7d82ca5c505d4b56fde68aa78ba7caf71b3ca2cf1598dddff528566a964/work"
            },
            "Name": "overlay2"
        },
        "Mounts": [],
        "Config": {
            "Hostname": "43147119c02a",
            "Domainname": "",
            "User": "",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "ExposedPorts": {
                "80/tcp": {}
            },
            "Tty": false,
            "OpenStdin": false,
            "StdinOnce": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "NGINX_VERSION=1.27.1",
                "NJS_VERSION=0.8.5",
                "NJS_RELEASE=1~bookworm",
                "PKG_RELEASE=1~bookworm",
                "DYNPKG_RELEASE=2~bookworm"
            ],
            "Cmd": [
                "nginx",
                "-g",
                "daemon off;"
            ],
            "Image": "nginx",
            "Volumes": null,
            "WorkingDir": "",
            "Entrypoint": [
                "/docker-entrypoint.sh"
            ],
            "OnBuild": null,
            "Labels": {
                "maintainer": "NGINX Docker Maintainers <docker-maint@nginx.com>"
            },
            "StopSignal": "SIGQUIT"
        },
        "NetworkSettings": {
            "Bridge": "",
            "SandboxID": "4c76fb8e97c6aca6858a8476d764d259fbebbb97c38b48f6b65a8bd8413eb165",
            "SandboxKey": "/var/run/docker/netns/4c76fb8e97c6",
            "Ports": {
                "80/tcp": null
            },
            "HairpinMode": false,
            "LinkLocalIPv6Address": "",
            "LinkLocalIPv6PrefixLen": 0,
            "SecondaryIPAddresses": null,
            "SecondaryIPv6Addresses": null,
            "EndpointID": "cbfee38857162451d749c7772167ac9d01c9fb844b76211aa41c0b239b384472",
            "Gateway": "172.17.0.1",
            "GlobalIPv6Address": "",
            "GlobalIPv6PrefixLen": 0,
            "IPAddress": "172.17.0.3",
            "IPPrefixLen": 16,
            "IPv6Gateway": "",
            "MacAddress": "02:42:ac:11:00:03",
            "Networks": {
                "bridge": {
                    "IPAMConfig": null,
                    "Links": null,
                    "Aliases": null,
                    "MacAddress": "02:42:ac:11:00:03",
                    "DriverOpts": null,
                    "NetworkID": "b6fbe659163bbccd7ffdace6cfe009584c698941994079fe9f9b3a34d360839c",
                    "EndpointID": "cbfee38857162451d749c7772167ac9d01c9fb844b76211aa41c0b239b384472",
                    "Gateway": "172.17.0.1",
                    "IPAddress": "172.17.0.3",
                    "IPPrefixLen": 16,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "DNSNames": null
                }
            }
        }
    }
]

We can also selectively query the inspect results hash using the -f or --format flag.

For example, let's retrieve the container network address:

docker container inspect -f '{{.NetworkSettings.IPAddress}}' nginx

172.17.0.3