Fuchsia

Zircon fundamentals

<<../../_common/intro/_zircon_intro.md>>

<<../../_common/intro/_zircon_syscall.md>>

<<../../_common/intro/_zircon_processes.md>>

<<../../_common/intro/_zircon_ipc.md>>

Exercise: Jobs and processes

Let‘s explore some of these fundamental concepts on a running system. In this exercise, you’ll see how jobs and processes interact to form a tree.

<<../_common/_start_femu.md>>

Dump the process list

Connect to a device shell prompt and use the ps command to dump the list of running jobs and processes.

fx shell ps

Below is a trimmed example of what the output looks like:

TASK                     PSS PRIVATE  SHARED   STATE NAME
j: 1027               507.8M  507.4M                 root
  p: 1061             564.4k    564k     36k         bin/bootsvc
  p: 1150            4264.4k   4264k     36k         bin/component_manager
  j: 1479             228.4k    228k
    p: 1583           228.4k    228k     36k         pwrbtn-monitor.cm
  j: 1484             532.4k    532k
    p: 1599           532.4k    532k     36k         svchost.cm
  j: 1544             402.4k    304k
    p: 1633           402.4k    304k    232k         netsvc.cm
  j: 1681             296.4k    296k
    p: 1733           296.4k    296k     36k         console-launcher.cm
  j: 1799            7232.4k   7232k
    p: 1825          7232.4k   7232k     36k         archivist.cm
  j: 1927             660.4k    660k
    p: 1955           660.4k    660k     36k         base-resolver.cm
  j: 2072            1016.4k   1016k
    p: 2088          1016.4k   1016k     36k         driver_manager.cm
  j: 2239             348.4k    348k
    p: 2252           348.4k    348k     36k         device-name-provider.cm
  j: 2364             275.3M  275.3M
    p: 2380          1012.4k   1012k     36k         fshost.cm
    p: 6544           252.1M  252.1M     36k         /pkg/bin/blobfs
    p: 10205         9744.4k   9744k     36k         /pkg/bin/minfs
    p: 10475           12.8M   12.8M     36k         pkgfs

Let's focus on two columns in the output for now:

  • TASK: This tells you whether each entry is a job (j) or process (p) followed by their unique id.
  • NAME: This provides a little more detail about what piece of the system is running there.

Let‘s break down some interesting things here based on what we’ve discussed so far:

  1. Every process is connected to a parent job. Some jobs have multiple processes.
  2. All jobs trace back to the root job as the ultimate parent, forming a tree.
  3. During startup, the system launches a few processes directly into the root job. Most other processes are launched under their own parent jobs.
  4. After the initial startup work, many of the entries have a .cm extension. These refer to components, and you will learn more about them later on.
  5. Some of these components are core services like filesystems (fshost.cm) and drivers (driver_manager.cm) that live in user space separate from the kernel.

Next, we‘ll explore how the Zircon enables the fundamentals of Fuchsia’s security model.