INITPHASE 1
Bootstrapping, System Management & Process Control
// invariant: you do not own a machine you cannot boot into by hand
Target Chapters
Ch 2Booting & System Management Daemons — UEFI, GRUB2, systemd, targets, emergency mode
Ch 4Process Control — lifecycle, SIGTERM vs SIGKILL, nice/renice, /proc/$PID
Technical Deep Dive — Kernel vs Userspace
The kernel hands control to PID 1 (systemd) which pivots userspace into a target. Unit definitions live in userspace at /etc/systemd/system/ but the *live* runtime graph is materialised under /run/systemd/system/. Never trust a unit file — inspect the running state. A process is a kernel object; its live descriptors, signals and scheduling class are all exposed as text under /proc/[PID].
/etc/systemd/system//proc/[PID]/status/run/systemd/system//proc/[PID]/fd/Interactive Labs & Break-Fix Runbooks
### SENIOR MENTOR DIRECTIVE
$ Stop reading man pages without inspecting live state. If you cannot drop into an emergency root shell from GRUB and remount a read-only filesystem as read-write, you do not own the machine. Never use SIGKILL (9) until you have proven SIGTERM (15) failed to clean up descriptors.