The Linux Kernel · Booting Linux

1. TODO 1: first_line
   fopen, fgets, fclose, cut the '\n'. Kernel: and Command line: appear.
2. TODO 2: field_kb
   Find "MemTotal:" in /proc/meminfo and read the number with sscanf.
3. TODO 3: read_stat
   After the last ')' in /proc/<pid>/stat: state, ppid … flags. One sscanf.
4. TODO 4: classify
   flags & PF_KTHREAD → kernel thread. Compare your counts with ps -ef.
5. Explore the lab PC
   uname -r; ls /boot; lsmod | wc -l; sudo dmesg | head; ulimit -s. Fill the table in the handout.
6. Think
   Why is cat /proc/uptime different every time, though no file changed? Write 3 sentences.

Submit: kinfo.c, its output on the lab PC, and the filled table. Keep kinfo: Lab 7.2 runs it as a child of your own init.

1. Get a kernel
   sudo cp /boot/vmlinuz-$(uname -r) vmlinuz && sudo chmod a+r vmlinuz: the lab PC's own kernel.
2. Boot the starter
   gcc -Wall -static -o init myinit_starter.c, ./mkinitramfs.sh, ./boot.sh. Read the panic: why?
3. TODO 1: mount
   Mount /proc and /sys. Now the kernel version and command line appear.
4. TODO 2: fork + exec
   Build kinfo with -static, run it as a child of your init, print its exit status.
5. TODO 3: never exit
   sync() and reboot(RB_POWER_OFF): QEMU powers off cleanly, no panic.
6. Experiments
   EXTRA=rdinit=/bin/kinfo ./boot.sh; EXTRA=nokaslr; boot with -m 128. Note what changes.

Quit a stuck QEMU with Ctrl-A then X. Submit: myinit.c and the serial output of your final boot.