sd_booted − Test whether the system is running the systemd init system.
sd_booted() checks whether the system was booted up using the systemd init system.
On failure, this call returns a negative errno−style error code. If the system was booted up with systemd as init system, this call returns a positive return value, zero otherwise.
This function is provided by the reference implementation of APIs for new−style daemons and distributed with the systemd package. The algorithm it implements is simple, and can easily be reimplemented in daemons if it is important to support this interface without using the reference implementation.
Internally, this function checks whether the /sys/fs/cgroup/systemd virtual file system is mounted, by comparing the st_dev value of the stat() data of /sys/fs/cgroup and /sys/fs/cgroup/systemd.
For details about the algorithm check the liberally licensed reference implementation sources: http://cgit.freedesktop.org/systemd/tree/src/sd-daemon.c resp. http://cgit.freedesktop.org/systemd/tree/src/sd-daemon.h
sd_booted() is implemented in the reference implementation's sd−daemon.c and sd−daemon.h files. These interfaces are available as shared library, which can be compiled and linked to with the libsystemd−daemon pkg-config(1) file. Alternatively, applications consuming these APIs may copy the implementation into their source tree. For more details about the reference implementation see sd_daemon(7).
If the reference implementation is used as drop−in files and −DDISABLE_SYSTEMD is set during compilation this function will always return 0 and otherwise become a NOP.
Lennart Poettering <firstname.lastname@example.org>
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