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.

Note: To ensure that you’re using the right version of ffx and fssh (which need to match the version of the SDK), consider updating your PATH to include the SDK‘s tools directory (for instance, export PATH="$PATH:$HOME/getting-started/tools"). However, if you don’t wish to update your PATH, ensure that you specify the relative path (for instance, tools/ffx) or absolute path (for instance, ~/getting-started/tools/ffx) to the tools in the SDK samples repository whenever you run these commands.

<<../_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.

fssh 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.