qemush/README.md

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# `qemush` - A suckless QEMU wrapper written in shell
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## How does it work
`qemush` allows to run commands as Unix user `qemu` to manage virtual machines and their disks associated.
## Why
`qemush` is **daemonless**: no bloaty long running process is needed for `qemush` to work.
`qemush` is **lightweight**: it only consists in a shell script to automate repeated tasks and force good practices.
`qemush` needs **few dependencies**: see section [Dependencies](#dependencies) for details.
`qemush` is **hackable**: you can [write your own launching scripts](#writing-a-launching-script) to make it work as intended.
`qemush` is **easy to setup**: you can make it work in a few steps, see section [Installation instructions](#installation-instructions).
## Good practices?
Here is a list of good practices forced by `qemush`.
- **Processes running as user `qemu`**: members of group `qemu` can manage the same virtual machines
- **Modularization**: `qemush` launching scripts are intended to be stackable to reuse common `qemu` parameters in all virtual machines needing them keep track of them
- **Copy-on-write**: images are formatted using `qcow2` to use less space on disk
- **Process detachment**: you can log out and have your virtual machines still running, control them via Unix sockets
## Is it better than `libvirt` ?
No. `qemush` and `libvirt` are for different use cases. `qemush` will allow you to spin up virtual machines really fast and with as little setup as possible, and aims to be nothing more than a QEMU wrapper, while `libvirt` will offer better out-of-the-box experience, with already existing pre-configurations, associated tools like the `virt-manager` GUI and a friendlier process supervision. You should use `qemush` if you care about controlling every aspect of your virtual machines, and are already used to using bare QEMU without an abstraction layer.
## Dependencies
From version 0.9.0, `qemush` is written in pure POSIX shell! The previous dependency on `bash` was removed in consequence.
All dependencies are common packages for a distribution, you'll be able to grab them from your favorite packages sources.
- `qemu` - this is literally a QEMU wrapper so there's a chance you'll need it
- `coreutils` - used for basic OS operations
- `sudo` - execute commands as `qemu`
- `socat` - monitor machines via Unix sockets
## Installation instructions
### QEMU user and group
`qemush` acts as Unix user `qemu` to manage virtual machines. You need to create a system user `qemu` that cannot login, with any home directory, in an Unix group of the same name. Example:
```sh
# Example if the qemu user doesn't exist
# Make sure /etc/shells contains /bin/nologin
useradd -r -s /bin/nologin qemu
```
For ease of use, you need to grant every user in the `qemu` group via `sudo` the right to execute commands as `qemu`. You can find an example `sudoers` rule in this repo's `etc/sudoers.d` folder.
### Via `Makefile` (recommended)
Just run the following command at the root of this repository to install `qemush` (previous step is **mandatory**) :
```sh
make
```
> And what if I don't want to bindly run this obscure `Makefile` ???
You'd be right. The next section is the exhaustive list of steps handled by the `Makefile` for the installation process.
### Manual installation (what does the `Makefile` do)
- Create `disks`, `launchers`, `shared`, `sockets/monitors`, `socket/spice` and `bin` directories in `~qemu`
- Copy `qemush` scripts parts from `qemu/bin` in `~qemu/bin` with mode `740`
- Compile C programs from `src` in `~qemu/bin` with mode `740`
- Copy the default launching scripts to `~qemu/launchers` with mode `740` ; this is optional but the one called `kvm` is the reference `qemush` launching script!
- Copy `bin/qemush` to `/usr/local/bin/qemush` with mode `755`
## Usage
### Writing a launching script
The default text editor used by `qemush` is `vi`, but it can be overriden by the `EDITOR` environment variable.
Run the following command to start editing a launching script by the name of your choice:
```sh
qemush edit "$name"
```
Example scripts are available in this repo's `qemu/launchers` folder.
### Launching a virtual machine
Virtual machines are identified by the name of their launching scripts. You can launch any machine with the following command:
```sh
qemush start "$name"
```
You can also list all available virtual machines by running this command:
```sh
qemush ls
```
### Other uses
You can show the full list of possible actions by running this command:
```sh
qemush help
```