containers / Toolbox

Toolbox is a tool for Linux operating systems, which allows the use of containerized command line environments. It is built on top of Podman and other standard container technologies from OCI.

This is particularly useful on OSTree based operating systems like Fedora CoreOS and Silverblue. The intention of these systems is to discourage installation of software on the host, and instead install software as (or in) containers — they mostly don't even have package managers like DNF or YUM. This makes it difficult to set up a development environment or install tools for debugging in the usual way.

Toolbox solves this problem by providing a fully mutable container within which one can install their favourite development and debugging tools, editors and SDKs. For example, it's possible to do yum install ansible without affecting the base operating system.

However, this tool doesn't require using an OSTree based system. It works equally well on Fedora Workstation and Server, and that's a useful way to incrementally adopt containerization.

The toolbox environment is based on an OCI image. On Fedora this is the fedora-toolbox image. This image is used to create a toolbox container that seamlessly integrates with the rest of the operating system by providing access to the user's home directory, the Wayland and X11 sockets, SSH agent, etc..

Installation

Toolbox is installed by default on Fedora Silverblue. On other operating systems it's just a matter of installing the toolbox package.

Usage

Create your toolbox container:

[[email protected] ~]$ toolbox create
Created container: fedora-toolbox-33
Enter with: toolbox enter
[[email protected] ~]$

This will create a container called fedora-toolbox-<version-id>.

Enter the toolbox:

[[email protected] ~]$ toolbox enter
⬢[[email protected] ~]$

Remove a toolbox container:

[[email protected] ~]$ toolbox rm fedora-toolbox-33
[[email protected] ~]$

Dependencies and Building

Toolbox requires at least Podman 1.4.0 to work, and uses the Meson build system.

The following dependencies are required to build it:

• meson
• go-md2man
• systemd
• go
• ninja

The following dependencies enable various optional features:

• bash-completion

It can be built and installed as any other typical Meson-based project:

[[email protected] toolbox]$ meson -Dprofile_dir=/etc/profile.d builddir
[[email protected] toolbox]$ ninja -C builddir
[[email protected] toolbox]$ sudo ninja -C builddir install

Toolbox is written in Go. Consult the src/go.mod file for a full list of all the Go dependencies.

By default, Toolbox uses Go modules and all the required Go packages are automatically downloaded as part of the build. There's no need to worry about the Go dependencies, unless the build environment doesn't have network access or any such peculiarities.

Distro support

By default, Toolbox creates the container using an OCI image called <ID>-toolbox:<VERSION-ID>, where <ID> and <VERSION-ID> are taken from the host's /usr/lib/os-release. For example, the default image on a Fedora 33 host would be fedora-toolbox:33.

This default can be overridden by the --image option in toolbox create, but operating system distributors should provide an adequately configured default image to ensure a smooth user experience.

Image requirements

Toolbox customizes newly created containers in a certain way. This requires certain tools and paths to be present and have certain characteristics inside the OCI image.

Tools:

• getent(1)
• id(1)
• ln(1)
• mkdir(1): for hosts where /home is a symbolic link to /var/home
• passwd(1)
• readlink(1)
• rm(1)
• rmdir(1): for hosts where /home is a symbolic link to /var/home
• sleep(1)
• test(1)
• touch(1)
• unlink(1)
• useradd(8)
• usermod(8)

Paths:

• /etc/host.conf: optional, if present not a bind mount
• /etc/hosts: optional, if present not a bind mount
• /etc/krb5.conf.d: directory, not a bind mount
• /etc/localtime: optional, if present not a bind mount
• /etc/resolv.conf: optional, if present not a bind mount
• /etc/timezone: optional, if present not a bind mount

Toolbox enables sudo(8) access inside containers. The following is necessary for that to work:

• The image should have sudo(8) enabled for users belonging to either the sudo or wheel groups, and the group itself should exist. File an issue if you really need support for a different group. However, it's preferable to keep this list as short as possible.

• The image should allow empty passwords for sudo(8). This can be achieved by either adding the nullok option to the PAM(8) configuration, or by add the NOPASSWD tag to the sudoers(5) configuration.

Since Toolbox only works with OCI images that fulfill certain requirements, it will refuse images that aren't tagged with com.github.containers.toolbox="true" and com.github.debarshiray.toolbox="true" labels. These labels are meant to be used by the maintainer of the image to indicate that they have read this document and tested that the image works with Toolbox. You can use the following snippet in a Dockerfile for this:

LABEL com.github.containers.toolbox="true" \
      com.github.debarshiray.toolbox="true"