Boot2podman is a lightweight Linux distribution made specifically to run Linux containers. It runs completely from RAM, is a ~90MB download.
- Recent Linux Kernel, Podman / Buildah pre-installed and ready-to-use
- Tools operate on Open Container Initiative (OCI) images and containers.
- Container persistence via disk automount on
/var/lib/containers - SSH keys persistence via disk automount (user keys and host keys)
- Linux 4.19, with support for
cgroupfsandoverlayfsconfigured - Podman and its dependencies like:
runc,conmon,cni-plugins - Varlink support for running remotely (being tunneled over SSH)
- Buildah support for building container images without daemon
Podman is a command line tool that allows for full management of a container's lifecycle from creation through removal. It supports multiple image formats including both the Docker and OCI image formats. Support for pods is provided allowing pods to manage groups of containers together.
Varlink is an interface description format and protocol that aims to make services accessible to both humans and machines in the simplest feasible way. A varlink interface has a reverse-domain name and specifies which methods the interface implements. Each method has named and typed input and output parameters.
The Buildah project provides a command line tool that be used to create an OCI or traditional Docker image format image and to then build a working container from the image. The container can be mounted and modified and then an image can be saved based on the updated container.
Skopeo is a command line tool that performs a variety of operations on container images and image repositories. Skopeo allows you to inspect an image showing its layers without requiring that the image be pulled. Skopeo also allows you to copy and delete an image from a repository.
For more details on the project relationship, see the Container Tools Guide.
ISO can be found in: https://github.com/boot2podman/boot2podman/releases
Note that if you use podman-machine, it will download the ISO automatically...
Please note that you should run podman and buildah using sudo!
In order to connect to the varlink socket (io.podman), you need root.
For now you need to mount the CD-ROM image (ISO) as IDE, not as SATA.
There is currently no support for the VirtualBox Guest Additions (vboxsf).
The default memory allocation (128 MiB) is too small to load everything:
qemu-system-x86_64 -enable-kvm -m 512 -cdrom boot2podman.iso
Here showing a simple login session, from an early development version:
The boot2podman logo is based on the original podman logo and the Montserrat font.
The text logo is based on http://ascii.co.uk/art/seal and figlet -f ascii12 podman.
Currently based on CorePure64-10.0.iso, but with a custom kernel (4.19.10 -> 4.19.28)
We need support for cgroupfs (including "memory") and for overlayfs (on ext4).
Also need memory cgroup swap enabled, otherwise memory limits won't work properly.
CONFIG_MEMCG=y
CONFIG_MEMCG_SWAP=y
CONFIG_MEMCG_SWAP_ENABLED=y
CONFIG_OVERLAY_FS=yWe install the required go compiler environment by building from source code.
Then we install podman and other dependencies by building from source code.
- runc
- conmon
- cni-plugins
- cgroupfs-mount
The varlink command line tool can be installed by building from source code.
Support for running containers as a non-root user by building from source code.
We can also add buildah and its dependencies, by building from source code.
Optionally also skopeo for remote operations, by building from source code.
Podman is run on a single host, Kubernetes is a cluster orchestration system.
We can install crio/crictl and k3s/kubectl by building from source code.
It is also possible to run the build commands (detailed above) using containers.
Note that you need to use tce-load -wic, if not running privileged (mount).
Except for the kernel and some system dependencies, everything uses packages.
Here are the binary packages that are produced, after building from source code.
These packages are used for building:
- compiletc.tcz 54M*
- gcc.tcz
- glibc_base-dev.tcz
- make.tcz
- pkg-config.tcz
- ...
- git.tcz 5.7M*
- go.tcz 75M*
* total size, including dependencies (see .tree and .dep)
These packages are used at runtime:
- podman.tcz 11M
- runc.tcz 2.8M
- conmon.tcz 24K
- cni-plugins.tcz 17M
- ...
- varlink.tcz 44K
- buildah.tcz 6M
- runc.tcz
- cni-plugins.tcz
- ...
These .tcz files are bundled with the kernel in a initramfs, as per remastering TC.
The software does not work after installation, without some mandatory registries and policy config done.
/etc/containers/registries.conf
[registries.search]
registries = ['docker.io', 'quay.io']
[registries.insecure]
registries = []
#blocked (docker only)
[registries.block]
registries = []{
"default": [
{
"type": "insecureAcceptAnything"
}
],
"transports":
{
"docker-daemon":
{
"": [{"type":"insecureAcceptAnything"}]
}
}
}/etc/containers/registries.d/default.yaml
# This is the default signature write location for docker registries.
default-docker:
# sigstore: file:///var/lib/atomic/sigstore
sigstore-staging: file:///var/lib/atomic/sigstoreWe need to make sure to use "cgroupfs" (not systemd) and to disable "pivot_root" (to run under tmpfs).
# CGroup Manager - valid values are "systemd" and "cgroupfs"
cgroup_manager = "cgroupfs"
# Whether to use chroot instead of pivot_root in the runtime
no_pivot_root = trueLocation of the configuration is currently hard-coded to /etc/containers, so it is not included in tcz...
Some information is currently not configurable, so it needs to be patched in to the source code directly.
Sample configuration, for /usr/local/etc/cni/net.d:
- bridge
- portmap
- loopback
Example config files can be found at these locations:
Boot2podman uses Tiny Core Linux, which runs from RAM and so does not persist filesystem changes by default.
When you run podman-machine create box, the tool auto-creates a disk that
will be automounted and used to persist your docker data in /var/lib/containers
and /var/lib/boot2podman. This virtual disk will be removed when you run
podman-machine delete box. It will also persist the SSH keys of the machine.
Changes outside of these directories will be lost after powering down or
restarting the VM.
If you are not using the Podman Machine management tool, you can create an ext4
formatted partition with the label boot2podman-data (mkfs.ext4 -L boot2podman-data /dev/sdX5) to your VM or host, and Boot2podman will automount
it on /mnt/sdX and then softlink /mnt/sdX/var/lib/containers to
/var/lib/containers.
Boot2podman is inspired by Boot2Docker, which is a similar solution but for another popular container runtime.