You can use a command in support of your answer, but we are evaluating your written response.

1. Shell B runs the ps command below while the game is running. What is the game’s PID, which process is its parent, and which terminal (Shell A or Shell B) is the game running in? How can you tell?

   $ ps -o user,pid,ppid,tty,stat,cmd -u ubuntu
   USER         PID    PPID TT       STAT CMD
   ubuntu      1402    1401 ?        S    sshd: ubuntu@pts/0
   ubuntu      1403    1402 pts/0    Ss   -bash
   ubuntu      1588    1403 pts/0    S+   nsnake
   ubuntu      1611    1610 ?        S    sshd: ubuntu@pts/1
   ubuntu      1612    1611 pts/1    Ss   -bash
   ubuntu      1650    1612 pts/1    R+   ps -o user,pid,ppid,tty,stat,cmd -u ubuntu
   

2. Using the output from question 1, a student runs kill -9 1588 from Shell B. Shell A returns to a prompt, but nothing the student types shows up on the screen. Why did this happen, and why is kill 1588 (without -9) usually the better first choice?

3. Given the jobs output below, a student runs kill 2 and gets bash: kill: (2) - Operation not permitted. What did the student actually try to kill, and how should they have referred to job 2?

   $ jobs
   [1]   Stopped                 nsnake
   [2]-  Stopped                 nsnake
   [3]+  Stopped                 nsnake
   

4. A student runs the game in Shell C and in a tmux session, then closes both ssh connections. After reconnecting, only the tmux game is still running. Using the pstree output below (taken before disconnecting), explain why.

   systemd─┬─...
        ├─sshd───sshd───sshd───bash───nsnake
        ├─sshd───sshd───sshd───bash───tmux: client
        ├─tmux: server───bash───nsnake
   

5. A student starts disk-watchdog with sudo systemctl start disk-watchdog and confirms it is running. After rebooting the instance, systemctl status shows the output below. Why isn’t the service running, and what command fixes it?

   ○ disk-watchdog.service - Disk usage watchdog
     Loaded: loaded (/etc/systemd/system/disk-watchdog.service; disabled; preset: enabled)
     Active: inactive (dead)
   

6. Given the output below, why did disk-watchdog.service fail to start?

   $ systemctl status disk-watchdog
   × disk-watchdog.service - Disk usage watchdog
     Loaded: loaded (/etc/systemd/system/disk-watchdog.service; enabled; preset: enabled)
     Active: failed (Result: exit-code)
    Process: 2210 ExecStart=/usr/local/bin/disk-watchdog.sh (code=exited, status=203/EXEC)
   $ ls -l /usr/local/bin/disk-watchdog.sh
   -rw-r--r-- 1 root root 812 Oct 20 11:04 /usr/local/bin/disk-watchdog.sh
   

7. To trigger the watchdog, a student runs truncate -s 5G bigfile. ls -lh bigfile shows 5.0G, but df -h / shows no change in usage and the watchdog never logs a warning. Why, and what command would actually spike disk usage?

8. A student creates a branch locally, makes a commit, and runs git push. Why does git respond with the output below?

   $ git push
   fatal: The current branch part2-compiling has no upstream branch.
   To push the current branch and set the remote as upstream, use
   
    git push --set-upstream origin part2-compiling
   

9. A student finishes Part 1 and wants to merge their work into main. They run the commands below. Why does main still not have the Part 1 changes, and what should they have done instead?

   $ git branch
     main
   * part1-compilers
   $ git merge main
   Already up to date.
   

10. While merging part1-compilers into main, a student sees the following in README.md. Which line came from which branch, and what steps finish the merge?

    <<<<<<< HEAD
    | **Java** | OpenJDK | `sudo apt install default-jdk` |
    =======
    | **Java** | OpenJDK | `sudo apt install openjdk-21-jdk` |
    >>>>>>> part1-compilers
    

11. A student adds Lab10/todo to the .gitignore in the root of their repository, rebuilds the program, and runs git status. Why is the executable still showing up, and how do they fix it?

    Changes not staged for commit:
        modified:   Lab10/todo
    

12. A project contains main.c, todo.c, and todo.h. add_task is declared in todo.h and defined in todo.c. Why does the command below fail, and how should it be fixed?

    $ gcc main.c -o todo
    /usr/bin/ld: /tmp/ccA1b2C3.o: in function `main':
    main.c:(.text+0x5e): undefined reference to `add_task'
    collect2: error: ld returned 1 exit status
    

13. A student clones a terminal game’s source code from GitHub and runs make. gcc --version works, so why does the build fail, and what is one way to fix it?

    $ make
    gcc -O2 -o snake snake.c -lncurses
    snake.c:3:10: fatal error: ncurses.h: No such file or directory
    3 | #include <ncurses.h>
      |          ^~~~~~~~~
    compilation terminated.
    

14. After fixing the build in question 13, ./snake runs from inside the repository folder, but typing snake from the home directory gives snake: command not found. Why, and what is one way to make snake run from any directory?

15. Given the Makefile below, a student runs make build twice in a row. The first run compiles, the second prints make: Nothing to be done for 'build'. After editing todo.c, make build compiles again. How does make decide when to rebuild? ```make build: todo

todo: main.c todo.c todo.h gcc main.c todo.c -o todo ```