Diagnostic and Debugging Tools

Question 1

What are diagnostic and debugging tools used for?

Answer 1

To inspect and troubleshoot running processes in Linux.

Question 2

What do these tools provide?

Answer 2

Real-time visibility into process behavior.

Question 3

Which tools are included?

Answer 3

/proc/<PID>, pstree, lsof, and strace.</PID>

Question 4

What does /proc/<PID> directory reveal?</PID>

Answer 4

Information about a specific process.

Question 5

What details can /proc/<PID> show?</PID>

Answer 5

Command line, environment variables, memory usage, and open file descriptors.

Question 6

Does /proc/<PID> require additional software?</PID>

Answer 6

No, it is built-in and updates live.

Question 7

Example of /proc usage?

Answer 7

/proc/2345/status shows memory usage.

Question 8

Another example of /proc usage?

Answer 8

/proc/2345/cmdline shows how the process was launched.

Question 9

Why is /proc useful?

Answer 9

Diagnosing resource issues.

Question 10

What does pstree command do?

Answer 10

Shows hierarchical diagram of processes.

Question 11

What relationships does pstree display?

Answer 11

Parent and child relationships.

Question 12

Why use pstree?

Answer 12

To track process lineage and investigate zombie processes.

Question 13

Option for pstree to include PIDs?

Answer 13

pstree -p.

Question 14

Example of pstree usage?

Answer 14

Verify if worker processes were respawned correctly after a web app update.

Question 15

What does lsof command do?

Answer 15

Lists all open files and the processes using them.

Question 16

What counts as files in Linux?

Answer 16

Sockets, pipes, and devices.

Question 17

Option for lsof to show network sockets?

Answer 17

lsof -i.

Question 18

Example of lsof usage for HTTPS?

Answer 18

sudo lsof -iTCP:443 -sTCP:LISTEN shows process listening on HTTPS.

Question 19

Example of lsof usage for a host?

Answer 19

lsof -i@192.168.1.100 lists connections to a host.

Question 20

Why use lsof?

Answer 20

Detect port conflicts, identify unauthorized daemons, verify firewall rules, and map network endpoints to PIDs.

Question 21

What does strace command do?

Answer 21

Hooks into a running process or starts one under trace and logs all system calls.

Question 22

What system calls does strace log?

Answer 22

open(), read(), write(), connect(), etc.

Question 23

Example of strace usage?

Answer 23

strace -e open,connect -p 3456 traces access attempts.

Question 24

Why use strace?

Answer 24

To find missing files, detect misconfigured permissions, diagnose subtle I/O errors, and gain detailed insight beyond logs.