ussefdesouky / embedded-linux

Embedded Linux

1. Linux Fundamentals

1.1. Linux System Architecture

2. System Call Interface

2.1. LAB

2.1.1. Trace $ ps command

$ strace -c ps

• Files of interactions NONE.
• Time taken by each syscall and syscall list can be found here by executing the command below.

$ strace -o ps_trace.txt -c ps

• Files of interaction ps_trace.txt.

2.1.2. Trace $ ls command

$ strace -c ls

• Files of interactions NONE.
• Time taken by each syscall and syscall list can be found here by executing the command below.

$ strace -o ls_trace.txt -c ls

• Files of interaction ls_trace.txt.

2.1.3. Trace $ cd command

$ strace -c cd

• Error: strace: Can't stat 'cd': No such file or directory
• Note: cd do not have an executable in the bin directory like ls and ps commands, because it's built in the shell.
• Solution: Trace a bash that runs the cd command
• Time taken by each syscall and syscall list can be found here by executing the command below.

$ strace -o cd_trace.txt -c sh -c "cd"

• Files of interaction: the directory you want to go, ex: Downloads and cd_trace.txt.

3. Process Management

3.1. LAB

3.1.1. Check how many cores.

$ top

• press 1 to list all the cores you have

3.1.2. Create number of cores + 2 processes dd if=/dev/zero of=/dev/null run in background.

$ for i in {1..22}; do dd if=/dev/zero of=/dev/null & done

3.1.3. Change priority for them

$ sudo renice -n 20 $(jobs -p)

3.1.4. Monitor them using top command

3.1.5. Kill them all using killall command.

$ killall dd

OR

$ kill $(jobs -p)

• Note: this will kill all the background processes.