lachlan / shawl

Windows service wrapper for arbitrary commands

Shawl

Shawl is a wrapper for running arbitrary programs as Windows services, written in Rust. It handles the Windows service API for you so that your program only needs to respond to ctrl-C/SIGINT. If you're creating a project that needs to run as a service, simply bundle Shawl with your project, set it as the entry point, and pass the command to run via CLI. Here is an example of creating a service wrapped with Shawl (note that -- separates Shawl's own options from the command that you'd like it to run):

• Using Shawl's add command:
  • shawl add --name my-app -- C:/path/my-app.exe
• Using the Windows sc command for more control:
  • sc create my-app binPath= "C:/path/shawl.exe run --name my-app -- C:/path/my-app.exe"
• Then start or configure the service as normal:

  • sc config my-app start= auto
    sc start my-app
    

Shawl will inspect the state of your program in order to report the correct status to Windows:

• By default, when your program exits, Shawl will restart it if the exit code is nonzero. You can customize this behavior with --(no-)restart for all exit codes or --restart-if(-not) for specific exit codes. Note that these four options are mutually exclusive.
• When the service is requested to stop, Shawl sends your program a ctrl-C event, then waits up to 3000 milliseconds (based on --stop-timeout) before forcibly killing the process if necessary.
• In either case, if Shawl is not restarting your program, then it reports the exit code to Windows as a service-specific error, unless the exit code is 0 or a code you've configured with --pass.

Shawl creates a log file for each service, shawl_for_<service>_*.log (based on the --name), in the same location as the Shawl executable, with both its own messages and the output from the commands that it runs. If anything goes wrong, you can read the log to find out more. You can disable all logging with --no-log, and you can disable just the command logs with --no-log-cmd. Each log file is limited to 2 MB, and up to 2 rotated copies will be retained.

Shawl differs from existing solutions like WinSW and NSSM in that they require running a special install command to prepare the service, which means, for example, that you have to run a CustomAction if you need to install a service in an MSI. With Shawl, you can configure the service however you want, such as with the normal ServiceInstall in an MSI or by running sc create, because Shawl doesn't have any special setup of its own. The shawl add command is just an optional convenience.

Bear in mind that the default account for new services is the Local System account, which has a different PATH environment variable than your user account. If you configure Shawl to run a command like npm start, that means npm needs to be in the Local System account's PATH, or you could also change the account used by the service instead.

Also note that running a service with a Local System account is as dangerous as running a Unix service as root. This greatly increases the risk of your system being hacked if you expose a port to the public for the service you are going to wrap. It is recommended that you use a restricted account, such as Network Service, to run services. To do this, first grant the Network Service account read, write, and execute permissions on Shawl’s installation directory, and then execute sc config my-app obj= "NT AUTHORITY\Network Service" password= "". If the service needs to read and write files, you may also need to grant the Network Service permissions to the directory that the service wants to access. More information about Windows service user accounts can be found here.

Installation

• Prebuilt binaries are available on the releases page. It's portable, so you can simply download it and put it anywhere without going through an installer.

• If you have Rust installed, you can run cargo install shawl.

• If you have Scoop, you can install by running:

  scoop bucket add extras
  scoop install shawl
  

  To update, run:

  scoop update
  scoop update shawl
  

CLI

You can view the command line help text in docs/cli.md.

Development

Please refer to CONTRIBUTING.md.