Getting Started
Learning Golang
If you are new to using Golang, you might find the following resources useful for getting started:
Understanding the Project Structure
The "entrypoint" of the Koble binary is through the cmd/kob package.
Under this we have the cli package, where our
Cobra root command is defined.
We also have the packages labs, machines and networks
for subcommands.
Within these packages there is a file for each command.
For example koble lab start is defined by startCmd in
cmd/kob/labs/start.go.
Most of the cobra commands are wrappers around functions defined by pkg/koble.
For example the RunE function of startCmd in cmd/kob/labs/start.go
calls cli.NK.LabStart(args),
where cli.NK is an instance of the Koble struct defined by pkg/koble.
The koble package is responsible for lab management, config, starting
and stopping etc.
This is similar to the job of lstart / vstart in
Netkit.
This package provides wrappers around driver functions for controlling
machines and networks.
Where possible,
cmd/kob should call functions from pkg/koble instead of pkg/driver.
The koble package should always call code from pkg/driver and NOT driver subpackages. This allows us to assure the abstraction between the driver interface and the workings of specific drivers.
The driver package in pkg/driver provides a Driver interface,
declaring functions which should be available for a struct to be a valid driver.
It also contains Machine and Network interfaces which need to be satisfied
by driver implementations.
The current driver implementations are uml and podman.
These contain structs which satisfy the Driver, Machine and Network
interfaces.
These are the key parts of how Koble runs virtual machines and networks.
Currently, the uml driver inherits much of its functionality from the podman
driver as it works by running a User-Mode Linux instance within a Podman container.
One way to navigate the project structure is to use the
Godoc Reference.
Starting at cmd you can easily navigate your way through the source code.
Additionally, using a tool or IDE where you can "jump to definition"
(GitHub has some level of this feature although not perfect),
is a huge help in navigating through source code,
especially in a large Go project with lots of packages.
Building the Koble Binary
To build the standard koble binary run:
plz build //cmd/kobThe koble binary can be found at plz-out/bin/cmd/kob/kob
To build the binary for systems which don’t have the correct glibc version:
CGO_ENABLED=0 go build -tags "exclude_graphdriver_btrfs btrfs_noversion exclude_graphdriver_devicemapper containers_image_openpgp" -o koble_linux_amd64 cmd/kob/*.goThe koble binary can be found at koble_linux_amd64.