Porting Guide/Tizen Bootup Overview
This section provides a brief overview of the typical booting sequence, starting from the boot loader to the kernel and the platform.
The Tizen bootup process is the same as any other Linux kernel. Just make sure that the correct machine ID and the boot arguments are passed from the boot loader.
After mounting the initial RAM disk image,
initramfs hands over the control to
systemd as system manager daemon in the Tizen platform. From this point,
systemd is responsible for probing all remaining hardware, mounting all necessary file systems and spawning all configured services. Basically system boot-up process is split up in various discrete steps. To synchronize point during start-up, target units (some file whose name ends in
.target) are used for grouping units. The boot-up process is highly parallelized in each target so that the order in which specific target units are reached is not deterministic. The
system-plugin-slp is an OAL plugin for configuration setting such as mount point (
The following figure shows the early boot sequence after starting the kernel.
- Special target unit for early boot-up scripts
- It has dependencies on necessary services and targets, such as
- At this point, most of file systems like <code>/opt,
/mediaare mounted and the
systemdrelated daemons, such as
- Special target unit for basic boot-up.
- At this point, all necessary initialization for general purpose daemons such as mount points, sockets, timers, and path units are completed.
- Tizen specific services (such as
tizen-debug-level) also are executed.
- Special target unit for selecting the boot mode.
- If kernel boot parameter (
/proc/cmdline) has the
charger_detect_bootoption passed by the boot loader such as
uboot, the platform boots up as charging mode. In this mode, the system enters the low power mode and charges the battery.
- If the
charger_detect_bootoption is not included as the kernel boot parameter, normal boot is started.
The following figure shows the overview of normal booting sequence in Tizen platform.
- Special target unit for setting up a multi-user system which is non-graphical support.
- In Tizen platform, this target is used for launching platform infrastructure daemons such as
dbus(system session), power manager, GPS manager, telephony daemon, WRT (Web Run Time) security daemon, and media server.
systemdrelated daemons (such as
systemd-logind) are also started in this phase.
- Special target unit for setting up a graphical environment.
- Some important daemons (such as access control server and OMA DS agent server) that must have root permission are launched at this point.
- Tizen platform uses the
systemduser session for App privilege daemons.
- Some daemons related with graphic system such as Enlightenment (Windows manager) are launched as App privilege in this phase.
- Tizen platform has its special target for middleware and mobile service:
tizen-middleware.targetstarts the platform service daemons, such as calendar, contacts, email, message, sound, and download provider.
tizen-mobile-session.targetstarts some service daemons related with the mobile session.