Adding user
--------------
	 > useradd ABC
	 > passwd ABC
	 > cat /etc/passwd

path created as /home/ABC

Username: User login name used to login into system. It should be between 1 to 32 charcters long.
Password: User password (or x character) stored in /etc/shadow file in encrypted format.
User ID (UID): Every user must have a User ID (UID) User Identification Number. By default UID 0 is reserved for root user and UID’s ranging from 1-99 are reserved for other predefined accounts. Further UID’s ranging from 100-999 are reserved for system accounts and groups.
Group ID (GID): The primary Group ID (GID) Group Identification Number stored in /etc/group file.
User Info: This field is optional and allow you to define extra information about the user. For example, user full name. This field is filled by ‘finger’ command.
Home Directory: The absolute location of user’s home directory.
Shell: The absolute location of a user’s shell i.e. /bin/bash.


User related:
-----------------
> whoami
root


Important files
----------------
/include/linux/sched.h
/kernel/sched.c


Tracing
-----------------
strace -i -p pid
strace -t -p pid -o out.txt


Path to kernel files
------------------
cd /usr/src/kernels/

Find a file
---------------
find -name fname



to see kernel messages printed by printk
-----------------------------
dmesg

check kernel version
---------------------
uname -r
cat /proc/version




Compiling the kernel
--------------------
cd /usr/src/kernels/some-kernel
make
make modules
make modules_install
make install


untar
=======
tar -xjf linux-tar-file

vim
===========
set nocompatible



Steps to create a system call
==============================
1.