linuxexpert-practice-labs/labs/linux-plus/2-3-1-viewing-processes/README.md

Linux+ 2.3.1: Looking at processes

Process states, zombies and their parents, finding a busy process with the sysstat tools, and tracing a program's system calls.

Before you start

The lab installs sysstat and strace, and starts some processes for you to find: one that is stopped, one whose child is a zombie, and one that keeps a CPU core busy. It also installs a small program, /usr/local/bin/lab-report. Write answers to the files in /root/lab-answers/. Leave the processes running until you've checked.

Tasks

1. Find the stopped process (state T), and write its PID to /root/lab-answers/1.
2. Find the zombie (state Z). Write the PID of its parent, the process that never collected it, to /root/lab-answers/2.
3. One process keeps a CPU core busy. Confirm it with mpstat and pidstat and write its PID to /root/lab-answers/3.
4. Trace /usr/local/bin/lab-report with strace to see which files it opens, and write the full path of the configuration file it reads to /root/lab-answers/4.

Hints

• ps -eo pid,ppid,stat,%cpu,%mem,cmd, pstree -ps PID.
• ps -eo pid,ppid,stat,cmd | grep '[d]efunct'; the parent is the PPID.
• mpstat -P ALL 1 3, pidstat 1 3, top.
• strace -f -e trace=openat COMMAND.