This tutorial will focus on seeing what is going on inside the containers you are running. There are several docker commands to do this with the most common ones being docker container top, docker container inspect, and docker container stats. The top command is a process list in one container. The inspect command is quite interesting as it provides the details of how a container started and how it is configured. The stats command can be used to look at all running container’s stats or one at a time in a real-time stream output to the terminal. Let’s look at some of these commands in action.
Spinning Up A Couple Containers
To test out the monitoring commands for docker containers, first, we need to spin up a few containers to work with. We’ve seen how to run multiple containers, so let’s bring a couple up again. We can launch an Nginx container, a MySQL container, and then list them in their running state.
$ docker container run -d --name nginx nginx d4f849b858a9df134f7f907c6e929c2ef1e89b86df8f851c8f209f6d6ac7a9e1 $ docker container run -d --name mysql -e MYSQL_RANDOM_ROOT_PASSWORD=true mysql e9263551f40fb30deb0b09434bf26697fce3eaf3370141d01c209d997c73885b $ docker container ls CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES e9263551f40f mysql "docker-entrypoint.s…" 26 seconds ago Up 25 seconds 3306/tcp, 33060/tcp mysql d4f849b858a9 nginx "/docker-entrypoint.…" 49 seconds ago Up 48 seconds 80/tcp nginx
Docker Container Top
In Linux, the top command is used to show the Linux processes. It provides a dynamic real-time view of the running system. We can do a similar thing in Docker.
$ docker container top nginx PID USER TIME COMMAND 1493 root 0:00 nginx: master process nginx -g daemon off; 1551 101 0:00 nginx: worker process $ docker container top mysql PID USER TIME COMMAND 1569 999 0:01 mysqld
Docker Container Inspect
The inspect command can be run on one or more images or containers. Either the name or id can be used to identify an image or container. Here we inspect the Nginx container in our environment. The output is in JSON format and contains literally all of the data about how the container was started.
$ docker container inspect nginx
[
{
"Id": "d4f849b858a9df134f7f907c6e929c2ef1e89b86df8f851c8f209f6d6ac7a9e1",
"Created": "2020-10-01T14:57:13.6068591Z",
"Path": "/docker-entrypoint.sh",
"Args": [
"nginx",
"-g",
"daemon off;"
],
"State": {
"Status": "running",
"Running": true,
"Paused": false,
"Restarting": false,
"OOMKilled": false,
"Dead": false,
"Pid": 1493,
"ExitCode": 0,
"Error": "",
"StartedAt": "2020-10-01T14:57:14.3647252Z",
"FinishedAt": "0001-01-01T00:00:00Z"
},
"Image": "sha256:7e4d58f0e5f3b60077e9a5d96b4be1b974b5a484f54f9393000a99f3b6816e3d",
"ResolvConfPath": "/var/lib/docker/containers/d4f849b858a9df134f7f907c6e929c2ef1e89b86df8f851c8f209f6d6ac7a9e1/resolv.conf",
"HostnamePath": "/var/lib/docker/containers/d4f849b858a9df134f7f907c6e929c2ef1e89b86df8f851c8f209f6d6ac7a9e1/hostname",
"HostsPath": "/var/lib/docker/containers/d4f849b858a9df134f7f907c6e929c2ef1e89b86df8f851c8f209f6d6ac7a9e1/hosts",
"LogPath": "/var/lib/docker/containers/d4f849b858a9df134f7f907c6e929c2ef1e89b86df8f851c8f209f6d6ac7a9e1/d4f849b858a9df134f7f907c6e929c2ef1e89b86df8f851c8f209f6d6ac7a9e1-json.log",
"Name": "/nginx",
"RestartCount": 0,
"Driver": "overlay2",
"Platform": "linux",
"MountLabel": "",
"ProcessLabel": "",
"AppArmorProfile": "",
"ExecIDs": null,
"HostConfig": {
"Binds": null,
"ContainerIDFile": "",
"LogConfig": {
"Type": "json-file",
"Config": {}
},
"NetworkMode": "default",
"PortBindings": {},
"RestartPolicy": {
"Name": "no",
"MaximumRetryCount": 0
},
"AutoRemove": false,
"VolumeDriver": "",
"VolumesFrom": null,
"CapAdd": null,
"CapDrop": null,
"Capabilities": null,
"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",
"ConsoleSize": [
30,
149
],
"Isolation": "",
"CpuShares": 0,
"Memory": 0,
"NanoCpus": 0,
"CgroupParent": "",
"BlkioWeight": 0,
"BlkioWeightDevice": [],
"BlkioDeviceReadBps": null,
"BlkioDeviceWriteBps": null,
"BlkioDeviceReadIOps": null,
"BlkioDeviceWriteIOps": null,
"CpuPeriod": 0,
"CpuQuota": 0,
"CpuRealtimePeriod": 0,
"CpuRealtimeRuntime": 0,
"CpusetCpus": "",
"CpusetMems": "",
"Devices": [],
"DeviceCgroupRules": null,
"DeviceRequests": null,
"KernelMemory": 0,
"KernelMemoryTCP": 0,
"MemoryReservation": 0,
"MemorySwap": 0,
"MemorySwappiness": null,
"OomKillDisable": false,
"PidsLimit": null,
"Ulimits": null,
"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"
],
"ReadonlyPaths": [
"/proc/bus",
"/proc/fs",
"/proc/irq",
"/proc/sys",
"/proc/sysrq-trigger"
]
},
"GraphDriver": {
"Data": {
"LowerDir": "/var/lib/docker/overlay2/6a6f3b5f81d2b454cbcc7651b3c40c90f8da991e9b55add4cfa8de2e3a57cd4d-init/diff:/var/lib/docker/overlay2/b873da3ee35fed4ed5b663d42705f29857e467ef7fc70d4f01b34e8593c90a2d/diff:/var/lib/docker/overlay2/c37b3ca864167a02502bc473d368823bdf2fdddf7ef3ff0fda126aae98ccf5c3/diff:/var/lib/docker/overlay2/d0b819fd09a7a62a2fc9858b4a015cd5594a240caefce77cad9a6b0f596f0dca/diff:/var/lib/docker/overlay2/5d3260b5420b271959560369b58594ca2be7fd8ae7bd74822c24c765c8ebeafc/diff:/var/lib/docker/overlay2/d874cfda684973a0d7f77e451987cd726723eab53aabf2ef285000ff32101e3d/diff",
"MergedDir": "/var/lib/docker/overlay2/6a6f3b5f81d2b454cbcc7651b3c40c90f8da991e9b55add4cfa8de2e3a57cd4d/merged",
"UpperDir": "/var/lib/docker/overlay2/6a6f3b5f81d2b454cbcc7651b3c40c90f8da991e9b55add4cfa8de2e3a57cd4d/diff",
"WorkDir": "/var/lib/docker/overlay2/6a6f3b5f81d2b454cbcc7651b3c40c90f8da991e9b55add4cfa8de2e3a57cd4d/work"
},
"Name": "overlay2"
},
"Mounts": [],
"Config": {
"Hostname": "d4f849b858a9",
"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=1.19.2",
"NJS_VERSION=0.4.3",
"PKG_RELEASE=1~buster"
],
"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": "SIGTERM"
},
"NetworkSettings": {
"Bridge": "",
"SandboxID": "ca6953bd7a7a11a50091be348a1414f9891d28fef9dcc241cc96332651fa0132",
"HairpinMode": false,
"LinkLocalIPv6Address": "",
"LinkLocalIPv6PrefixLen": 0,
"Ports": {
"80/tcp": null
},
"SandboxKey": "/var/run/docker/netns/ca6953bd7a7a",
"SecondaryIPAddresses": null,
"EndpointID": "2044cf6b4ded03757b71a40d21b727f0287ac1b1c1f5edbe1f767d5fffa67456",
"Gateway": "172.17.0.1",
"GlobalIPv6Address": "",
"GlobalIPv6PrefixLen": 0,
"IPAddress": "172.17.0.2",
"IPPrefixLen": 16,
"IPv6Gateway": "",
"MacAddress": "02:42:ac:11:00:02",
"Networks": {
"bridge": {
"IPAMConfig": null,
"Links": null,
"Aliases": null,
"NetworkID": "0099dce04d4e730d272d5c774970a65704c8df6869dfadba2c2363e532c4caf9",
"EndpointID": "2044cf6b4ded03757b71a40d21b727f0287ac1b1c1f5edbe1f767d5fffa67456",
"Gateway": "172.17.0.1",
"IPAddress": "172.17.0.2",
"IPPrefixLen": 16,
"IPv6Gateway": "",
"GlobalIPv6Address": "",
"GlobalIPv6PrefixLen": 0,
"MacAddress": "02:42:ac:11:00:02",
"DriverOpts": null
}
}
}
}
]
Filtering Inspect Output
Since the output is so large, you can pipe the results to either Select-String in Powershell, or grep in bash. For example:
$ docker container inspect nginx | Select-String -Pattern IPAddress
"SecondaryIPAddresses": null,
"IPAddress": "172.17.0.2",
"IPAddress": "172.17.0.2",
Docker Container Stats
When using the stats command, you can view all running containers together, or specify just one container you want to look at. The output is live streaming data that updates in real-time with the cpu, memory, io, and so on.
$ docker container stats CONTAINER ID NAME CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS e9263551f40f mysql 0.13% 332MiB / 6.087GiB 5.33% 866B / 0B 0B / 0B 38 d4f849b858a9 nginx 0.00% 3.973MiB / 6.087GiB 0.06% 1.05kB / 0B 0B / 0B 2
$ docker container stats nginx CONTAINER ID NAME CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS d4f849b858a9 nginx 0.00% 3.973MiB / 6.087GiB 0.06% 1.05kB / 0B 0B / 0B 2
$ docker container stats mysql CONTAINER ID NAME CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS e9263551f40f mysql 1.98% 332MiB / 6.087GiB 5.33% 866B / 0B 0B / 0B 38
Learn More
- Thenewstack.io Identifying Collecting Container Data (thenewstack.io)
- Docker Container Monitoring (sematext.com)
- Best Docker Container Monitoring Tools (comparitech.com)
- Technologies Docker Monitoring (dynatrace.com)
- Top Docker Monitoring Tools (code-maze.com)
- Container Monitoring Tools (dnsstuff.com)
- Docker Monitoring Explained Monitor Containers Microservices (bmc.com)
- Comparing Monitoring Options For Docker Deployments (rancher.com)
- How To Monitor Your Docker Containers With Ctop (techrepublic.com)
- Azure Monitor Insights Containers (docs.microsoft.com)
Docker Monitoring Commands Summary
We now know how to use the docker container top command to list all the processes that will be running in a single container. We also learned about docker container inspect to see how the container was run and what its options and configuration are. The docker container stats command showed gave us a live updating output to the terminal of CPU usage, Memory usage, Net IO, and Block IO.
| docker container top | Display the running processes of a container |
| docker container inspect | Display detailed information on one or more containers |
| docker container stats | Display a live stream of container(s) resource usage statistics |
