How to use the features of container.
Since the containers created by container are lightweight virtual machines, consider the needs of your containerized application when you use container run. The --memory and --cpus options allow you to override the default memory and CPU limits for the virtual machine. The default values are 1 gigabyte of RAM and 4 CPUs. You can use abbreviations for memory units; for example, to run a container for image big with 8 CPUs and 32 gigabytes of memory, use:
container run --rm --cpus 8 --memory 32g bigWhen you first run container build, container starts a builder, which is a utility container that builds images from your Dockerfiles. As with anything you run with container run, the builder runs in a lightweight virtual machine, so for resource-intensive builds, you may need to increase the memory and CPU limits for the builder VM.
By default, the builder VM receives 2 gigabytes of RAM and 2 CPUs. You can change these limits by starting the builder container before running container build:
container builder start --cpus 8 --memory 32gIf your builder is already running and you need to modify the limits, just stop, delete, and restart the builder:
container builder stop
container builder delete
container builder start --cpus 8 --memory 32gWith the --volume option of container run, you can share data between the host system and one or more containers, and you can persist data across multiple container runs. The volume option allows you to mount a folder on your host to a filesystem path in the container.
This example mounts a folder named assets on your Desktop to the directory /content/assets in a container:
% ls -l ~/Desktop/assets
total 8
-rw-r--r--@ 1 fido staff 2410 May 13 18:36 link.svg
% container run --volume ${HOME}/Desktop/assets:/content/assets docker.io/python:alpine ls -l /content/assets
total 4
-rw-r--r-- 1 root root 2410 May 14 01:36 link.svg
%
The argument to --volume in the example consists of the full pathname for the host folder and the full pathname for the mount point in the container, separated by a colon.
The --mount option uses a comma-separated key=value syntax to achieve the same result:
% container run --mount source=${HOME}/Desktop/assets,target=/content/assets docker.io/python:alpine ls -l /content/assets
total 4
-rw-r--r-- 1 root root 2410 May 14 01:36 link.svg
%
Using the project from the tutorial example, you can create an image to use both on Apple silicon Macs and on x86-64 servers.
When building the image, just add --arch options that direct the builder to create an image supporting both the arm64 and amd64 architectures:
container build --arch arm64 --arch amd64 --tag registry.example.com/fido/web-test:latest --file Dockerfile .Try running the command uname -a with the arm64 variant of the image to see the system information that the virtual machine reports:
% container run --arch arm64 --rm registry.example.com/fido/web-test:latest uname -a Linux 7932ce5f-ec10-4fbe-a2dc-f29129a86b64 6.1.68 #1 SMP Mon Mar 31 18:27:51 UTC 2025 aarch64 GNU/Linux %
When you run the command with the amd64 architecture, the x86-64 version of uname runs under Rosetta translation, so that you will see information for an x86-64 system:
% container run --arch amd64 --rm registry.example.com/fido/web-test:latest uname -a Linux c0376e0a-0bfd-4eea-9e9e-9f9a2c327051 6.1.68 #1 SMP Mon Mar 31 18:27:51 UTC 2025 x86_64 GNU/Linux %
The command to push your multiplatform image to a registry is no different than that for a single-platform image:
container images push registry.example.com/fido/web-test:latestcontainer images list and container list provide basic information for all of your images and containers. You can also use list and inspect commands to print detailed JSON output for one or more resources.
Use the inspect command and send the result to the jq command to get pretty-printed JSON for the images or containers that you specify:
% container images inspect web-test | jq
[
{
"name": "web-test:latest",
"variants": [
{
"platform": {
"os": "linux",
"architecture": "arm64"
},
"config": {
"created": "2025-05-08T22:27:23Z",
"architecture": "arm64",
...
% container inspect my-web-server | jq
[
{
"status": "running",
"networks": [
{
"address": "192.168.64.3/24",
"gateway": "192.168.64.1",
"hostname": "my-web-server.test.",
"network": "default"
}
],
"configuration": {
"mounts": [],
"hostname": "my-web-server",
"id": "my-web-server",
"resources": {
"cpus": 4,
"memoryInBytes": 1073741824,
},
...
Use the list command with the --format option to display information for all images or containers. In this example, the --all option shows stopped as well as running containers, and jq selects the IP address for each running container:
% container ls --format json --all | jq '.[] | select ( .status == "running" ) | [ .configuration.id, .networks[0].address ]' [ "my-web-server", "192.168.64.3/24" ] [ "buildkit", "192.168.64.2/24" ]
Use the --publish option to forward TCP or UDP traffic from your loopback IP to the container you run. The option value has the form [host-ip:]host-port:container-port[/protocol], where protocol may be tcp or udp, case insensitive.
If your container attaches to multiple networks, the ports you publish forward to the IP address of the interface attached to the first network.
To forward requests from localhost:8080 to a Python webserver on container port 8000, run:
container run -d --rm -p 127.0.0.1:8080:8000 python:slim python3 -m http.server --bind 0.0.0.0 8000A curl to localhost:8000 outputs:
% curl http://localhost:8080
<!DOCTYPE HTML>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Directory listing for /</title>
</head>
<body>
<h1>Directory listing for /</h1>
<hr>
<ul>
<li><a href="bin/">bin@</a></li>
<li><a href="boot/">boot/</a></li>
<li><a href="dev/">dev/</a></li>
<li><a href="etc/">etc/</a></li>
<li><a href="home/">home/</a></li>
<li><a href="lib/">lib@</a></li>
<li><a href="lost%2Bfound/">lost+found/</a></li>
<li><a href="media/">media/</a></li>
<li><a href="mnt/">mnt/</a></li>
<li><a href="opt/">opt/</a></li>
<li><a href="proc/">proc/</a></li>
<li><a href="root/">root/</a></li>
<li><a href="run/">run/</a></li>
<li><a href="sbin/">sbin@</a></li>
<li><a href="srv/">srv/</a></li>
<li><a href="sys/">sys/</a></li>
<li><a href="tmp/">tmp/</a></li>
<li><a href="usr/">usr/</a></li>
<li><a href="var/">var/</a></li>
</ul>
<hr>
</body>
</html>Note
This feature is available on macOS 26 and later.
Running container system start creates a vmnet network named default to which your containers will attach unless you specify otherwise.
You can create a separate isolated network using container network create.
This command creates a network named foo:
container network create fooThe foo network, the default network, and any other networks you create are isolated from one another. A container on one network has no connectivity to containers on other networks.
Run container network list to see the networks that exist:
% container network list
NETWORK STATE SUBNET
default running 192.168.64.0/24
foo running 192.168.65.0/24
%Run a container that is attached to that network using the --network flag:
container run -d --name my-web-server --network foo --rm web-testUse container ls to see that the container is on the foo subnet:
% container ls
ID IMAGE OS ARCH STATE ADDR
my-web-server web-test:latest linux arm64 running 192.168.65.2You can delete networks that you create once no containers are attached:
container stop my-web-server
container network delete fooThe container logs command displays the output from your containerized application:
% container run -d --name my-web-server --rm registry.example.com/fido/web-test:latest my-web-server % curl http://my-web-server.test <!DOCTYPE html><html><head><title>Hello</title></head><body><h1>Hello, world!</h1></body></html> % container logs my-web-server 192.168.64.1 - - [15/May/2025 03:00:03] "GET / HTTP/1.1" 200 - %
Use the --boot option to see the logs for the virtual machine boot and init process:
% container logs --boot my-web-server [ 0.098284] cacheinfo: Unable to detect cache hierarchy for CPU 0 [ 0.098466] random: crng init done [ 0.099657] brd: module loaded [ 0.100707] loop: module loaded [ 0.100838] virtio_blk virtio2: 1/0/0 default/read/poll queues [ 0.101051] virtio_blk virtio2: [vda] 1073741824 512-byte logical blocks (550 GB/512 GiB) ... [ 0.127467] EXT4-fs (vda): mounted filesystem without journal. Quota mode: disabled. [ 0.127525] VFS: Mounted root (ext4 filesystem) readonly on device 254:0. [ 0.127635] devtmpfs: mounted [ 0.127773] Freeing unused kernel memory: 2816K [ 0.143252] Run /sbin/vminitd as init process 2025-05-15T02:24:08+0000 info vminitd : [vminitd] vminitd booting... 2025-05-15T02:24:08+0000 info vminitd : [vminitd] serve vminitd api 2025-05-15T02:24:08+0000 debug vminitd : [vminitd] starting process supervisor 2025-05-15T02:24:08+0000 debug vminitd : port=1024 [vminitd] booting grpc server on vsock ... 2025-05-15T02:24:08+0000 debug vminitd : exits=[362: 0] pid=363 [vminitd] checking for exit of managed process 2025-05-15T02:24:08+0000 debug vminitd : [vminitd] waiting on process my-web-server [ 1.122742] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready 2025-05-15T02:24:39+0000 debug vminitd : sec=1747275879 usec=478412 [vminitd] setTime %
Note
This feature requires a M3 or newer Apple silicon machine and a Linux kernel that supports virtualization. For a kernel configuration that has all of the right features enabled, see https://github.com/apple/containerization/blob/0.5.0/kernel/config-arm64#L602.
You can enable virtualization capabilities in containers by using the --virtualization option of container run and container create.
If your machine does not have support for nested virtualization, you will see the following:
container run --name nested-virtualization --virtualization --kernel /path/to/a/kernel/with/virtualization/support --rm ubuntu:latest sh -c "dmesg | grep kvm"
Error: unsupported: "nested virtualization is not supported on the platform"When nested virtualization is enabled successfully, dmesg will show output like the following:
container run --name nested-virtualization --virtualization --kernel /path/to/a/kernel/with/virtualization/support --rm ubuntu:latest sh -c "dmesg | grep kvm"
[ 0.017245] kvm [1]: IPA Size Limit: 40 bits
[ 0.017499] kvm [1]: GICv3: no GICV resource entry
[ 0.017501] kvm [1]: disabling GICv2 emulation
[ 0.017506] kvm [1]: GIC system register CPU interface enabled
[ 0.017685] kvm [1]: vgic interrupt IRQ9
[ 0.017893] kvm [1]: Hyp mode initialized successfullycontainer uses macOS user defaults to store configuration settings that persist between sessions. You can customize various aspects of container behavior, including build settings, default images, and network configuration.
For a complete list of available configuration options and detailed usage instructions, see the user defaults documentation.
If you want to prevent the use of Rosetta translation during container builds on Apple Silicon Macs:
defaults write com.apple.container.defaults build.rosetta -bool falseThis is useful when you want to ensure builds only produce native arm64 images and avoid any x86_64 emulation.
The container system logs command allows you to look at the log messages that container writes:
% container system logs | tail -8 2025-06-02 16:46:11.560780-0700 0xf6dc5 Info 0x0 61684 0 container-apiserver: [com.apple.container:APIServer] Registering plugin [id=com.apple.container.container-runtime-linux.my-web-server] 2025-06-02 16:46:11.699095-0700 0xf6ea8 Info 0x0 61733 0 container-runtime-linux: [com.apple.container:RuntimeLinuxHelper] starting container-runtime-linux [uuid=my-web-server] 2025-06-02 16:46:11.699125-0700 0xf6ea8 Info 0x0 61733 0 container-runtime-linux: [com.apple.container:RuntimeLinuxHelper] configuring XPC server [uuid=my-web-server] 2025-06-02 16:46:11.700908-0700 0xf6ea8 Info 0x0 61733 0 container-runtime-linux: [com.apple.container:RuntimeLinuxHelper] starting XPC server [uuid=my-web-server] 2025-06-02 16:46:11.703028-0700 0xf6ea8 Info 0x0 61733 0 container-runtime-linux: [com.apple.container:RuntimeLinuxHelper] `bootstrap` xpc handler [uuid=my-web-server] 2025-06-02 16:46:11.720836-0700 0xf6dc3 Info 0x0 61689 0 container-network-vmnet: [com.apple.container:NetworkVmnetHelper] allocated attachment [hostname=my-web-server.test.] [address=192.168.64.2/24] [gateway=192.168.64.1] [id=default] 2025-06-02 16:46:12.293193-0700 0xf6eaa Info 0x0 61733 0 container-runtime-linux: [com.apple.container:RuntimeLinuxHelper] `start` xpc handler [uuid=my-web-server] 2025-06-02 16:46:12.368723-0700 0xf6e93 Info 0x0 61684 0 container-apiserver: [com.apple.container:APIServer] Handling container my-web-server Start. %
The container --generate-completion-script [zsh|bash|fish] command generates completion scripts for the provided shell.
A detailed guide on how to install the completion scripts can be found here