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https://github.com/stephank/lazyssh

A jump-host SSH server that starts machines on-demand
https://github.com/stephank/lazyssh

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A jump-host SSH server that starts machines on-demand

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# LazySSH



LazySSH is an SSH server that acts as a jump host only, and dynamically starts

temporary virtual machines.



If you find yourself briefly starting a virtual machine just to SSH into it and

try something out, LazySSH is an attempt to automate that flow via just the

`ssh` command. LazySSH starts the machine for you when you connect, and shuts

it down (some time after) you disconnect.



Another possible use is to have LazySSH sit in front of a build server to start

specific types of machines for your build. (Think different CPU architectures

or operating systems.)



**Important**: LazySSH is a young piece of code. If you're going to use it to

create resources that cost money (like AWS EC2 instances), keep a close eye on

usage. If, for example, you put your laptop to sleep at the wrong time, or

LazySSH crashes for whatever reason, it may leave resources running.



**Important**: The security of LazySSH has not been tested in any way, so it's

probably best to run it in a closed setting. (Not facing the public internet or

otherwise firewalled.) The SSH server implementation is based on

[golang.org/x/crypto].



License: AGPL v3



[golang.org/x/crypto]: https://pkg.go.dev/golang.org/x/crypto



## Usage



There are several ways to get LazySSH:



- Grab a binary from the [releases page].



- Docker images are available on Docker Hub as

  [stephank/lazyssh](https://hub.docker.com/r/stephank/lazyssh).



- Nix users, whether you use flakes or not, see the documentation in

  [flake.nix](./flake.nix).



- If you instead want to build LazySSH yourself, you need at least Go 1.13,

  then just `go build`.



[releases page]: https://github.com/stephank/lazyssh/releases



You need to generate an SSH host key and client key. The host key is what the

server uses to identify itself, while the client key is what you connect with.



```sh

# Both of these also generate a .pub file with the public half of the key pair.

ssh-keygen -t ed25519 -f lazyssh_host_key

ssh-keygen -t ed25519 -f lazyssh_client_key

```



Now create a `config.hcl` file that looks like:



```hcl

server {

  # Set this to the contents of lazyssh_host_key generated above.

  host_key = <<-EOF

    -----BEGIN OPENSSH PRIVATE KEY-----

    [...]

    -----END OPENSSH PRIVATE KEY-----

  EOF



  # Set this to the contents of lazyssh_client_key.pub generated above.

  authorized_key = <<-EOF

    ssh-ed25519 [...]

  EOF

}

```



The `server` block is followed by one or more `target` blocks. Here are the

types of targets currently supported, and links to the documentation:



- [AWS EC2](./doc/providers/aws_ec2.md)

- [VirtualBox](./doc/providers/virtualbox.md)

- [Hetzner Cloud](./doc/providers/hcloud.md)

- [Dummy forwarding](./doc/providers/forward.md)



Once your config is ready, you can start the server:



```sh

./lazyssh -config ./config.hcl

```



> Using Docker? You can start the container with, for example:

>

> ```sh

> docker run \

>   -p 7922:7922 \

>   -v /path/to/config.hcl:/config.hcl:ro \

>   stephank/lazyssh

> ```



You usually need an entry for LazySSH in your `~/.ssh/config`, because the

`ssh` command otherwise doesn't make all options available for jump-hosts. Here

is a sample config:



```

Host lazyssh

  Hostname localhost

  Port 7922

  User jump

  PreferredAuthentications publickey

  IdentityFile ~/path/to/lazyssh_client_key

  IdentitiesOnly yes

```



Now you should be ready to go:



```sh

ssh -J lazyssh user@mytarget

```



For more details, see [the included documentation](./doc/index.md).