node-os Init

The init process, typically /sbin/init, is a long-lived process started by the kernel during boot. Init is responsible for starting system daemons such as sshd, getty, and dhcp.

On Ubuntu the init daemon is Upstart. Upstart, like most init daemons, has the concept of a system runlevel numbered 0-5. When init starts, it uses the runlevel to decide how to boot the system. The startup sequence involves parsing files in /etc/rcX.d, /etc/init, and /etc/init.d.

The node-os init daemon takes a different approach. The init daemon does nothing except basic job control.

• Init starts an HTTP server on 127.0.0.1:1 that can be used to start and stop jobs.
• Init hands control to another process that uses the API to boot the system as desired.
• Init itself does not parse config files.

API

GET    /jobs               <-- list all jobs
POST   /job                <-- start a job
PUT    /job/:id            <-- start a job with a specific name
PUT    /job/:id/sig/:sig   <-- signal a process
GET    /job/:id            <-- get job info
DELETE /job/:id            <-- clear a stopped job

Starting a job requires a JSON payload

{
  "exec": "node",
  "args": [ "server.js" ],
  "cwd" : "/var/www",
  "envs": {
    "PORT": "80",
    "PATH": "/bin:/root/bin"
  },
  "user": "www",
  "group": "www"
}

Todo

• restart semantics
• handling stdio
• pre-opened file-descriptors
• authentication and access control

Usage

init [next command and args]

After init starts its HTTP server, it passes the task of booting the system off to another process. You specify the next process by passing the command to init during start. These parameters can, and should, be passed to init by grub.

The next command effectively decides what order to boot system daemons in. The npkg command defined in node-os-npkg provides a nice interface between init and NodeJS packages installed on the system.