Learn Red Hat Linux.

2. In 1969, Four programmer Ken Thompson, Dennis Ritchie, Rudd Canady &
Doug McElroy made a program in Bell labs which does not have any name in
year 1969.
Brian Kernighan checked that program & found it is very good software for
client & networking purpose. He gave the name Unix to this program on 1st
January 1970 (epoch time).
First Operating System. That time that program was written in Assembly
language.
In 1972, a programmer Dennis Ritchie started converting this program in C
language. (Also called founder of C language).
1973- Unix in C language.

3. Paul Allen & Bill Gates are the employee of Bell Labs.
In 1981, they both started Microsoft with 9 more candidates & they gave a
programme named Xenix (1980) but it was flopped.
In 1981- Launched MS-DOS 1.0
In 1984- UNIX open source
In 1985- First Graphical Based OS- Win 2.0
In 1991, Linus Benedict Torvalds, B-tech Iind
year Computer Science, 23
years old student of University of Helensiki (Finland) made Kernel (25th
August 1991).
In 1994- Red Hat Company (collection of Linux Sets) came into existence.
96.8 % servers of Linux till 2009.

4. Everything is a file.
Small, single purpose programmes.
Ability to Chain programmes together to perform complex tasks.
Avoid captive user interfaces.
Configuration data stored in text.

5.  CPU
Min- Intel Pentium 4 2.0GHz
Rec- Intel Duel Core 2.0GHz
 RAM
Min- 512MB (Graphical) 384MB (CLI)
Rec- 1GB
 Hard Disk
Min- 4.5GB, Rec- 10GB

6.  4GB RAM – 2GB Swap
 4-16GB RAM- 4GB Swap
 16-64GB RAM- 8GB Swap
 / - Root Partition
 /boot – Boot Partition
 /swap - swap partition
 /home – Home Partition

7.  /home - Users home (all users folders)
 /bin, /usr/bin - Commands (user executable & Scripts)
 /sbin, /usr/sbin - root privileged command
 /usr - User’s Configurations files
 /etc - System Configuration files
 /boot - Linux Kernel & Bootable files
 /root - root (Admin) Data
 /mnt - for mounting any external devices
 /media - for mounting CD/DVD drives
 /dev - devices (HDD, CD-ROM, Pen Drive)
 /var, - Log files
 /proc - Current running system Information
 /sys - System Hardware Files
 /lib - Library files stored – All commands
 /net - Accessing Network File system
 /misc - Files for Auto-Mounting
 /opt - Optional software
 /tmp - Temporary files
 /srv - Server Database

8.  Post LILO (RHEL4)
 Boot Loader
GRUB (RHEL 5)
 Kernel (Vmlinuz)
 initrd (All device file information)
 init (Run Level)

9. Directory commands:
 mkdir <Directory name> - For creating directory.
 cd <Directory name> - change directory.
 cd .. - to come out from working directory.
 rmdir <Directory name> - to remove directory

10. File Commands:
 touch <filename> - creates a blank file.
 cat > filename - creates a file and for saving this file (ctrl + D)
 cat - to see the content of the file.
 cat file1 >> file2 - to move file1 matter in file2
 cat -n filename - to see how many lines are written in that file.

11. Commands for deleting:
 rm filename - deletes a file.
 rm -i - deletes file/folder in interactive mode (asking mode)

12. Help Commands:
 whatis <command>
man <command>
 info <command>
 <command> --help
 which <command>
 cd /usr/share/doc
These Commands are used as help commands.
Print all tags and summary of the asked command.

13. Copy:
 cp <source> <destination> - copies files from source to destination
 cp -i <source> <destination> - copies files from source to destination in asking
mode
 cp -i * <destination> - copies current working directory all data to
destination.
 cp -r <directory name> <destination> - copies directory from source to
destination

14. Rename & Move:
mv <oldfile> <newfile> (Rename)
mv <filename> <where we have to move the file> (Move)
Listing Commands:
 ls - listing files/folders
 ls -l (ll) - long listing of files/folders with whole information
 ls -a - lists all files/folders (hidden also)
 ls ??? - all files/folders named with 3 characters
 ls m* - files & directories started with letter m.

15.  poweroff -f
 halt -n -p - We can turn off our system by these
commands
 init 0
 init 6 - We can Restart our system by these
commands
 reboot
 startx - Switch from command to graphic.
 init 5 - Restart System graphically.
 history - To see history of recent commands.
 history -c - To clear the history of recent commands
 bc - Starts basic calculator.
 whoami or w - To know by which user we logged on

16.  mkfs.vfat -I /dev/device id - To format device in fat format
 look <word> - For looking the exact word spelling.
 date mmddhhmmyy - To set date.
 uname - To see kernel name.
 uname –r - Kernel release.
 uname –a - Whole information about kernel.
 file <file/directory name> - To check whether it is file or folder.
 cat > /etc/issue - To create logoff scripts.
 cat > /etc/motd - To create logon scripts.
 cal yyyy or mm yyyy - shows calendar of that month & year.

17.  adduser <username> - To create user
 passwd <username> - To give password to user.
 userdel (-r) <username> - To delete user.
 groupadd <name> - To add a group.
 usermod -G <group> <user> - It will add user to group.
 groupdel <name> - To delete group.
 chage -E YYYY-MM-DD <user> - Set user expiration.
 chage -l <username> - To see user detailed information.
 chage -W 1 <username> - To set warning period for user.
 usermod -L <username> - To lock a user account.
 usermod -U <username> - To unlock a user account.
 passwd -d <username> - To remove password for a user.

18. _ _ _ _ _ _ _ _ _ _ owner group filename
f/d User group others
r=4 (22
) w=2 (21
) x=1 (20
)
read write execute
For directory maximum permission = 777
For files maximum permission = 666
Default permission for file = 644
Default permission for directory = 755

19. To give user full permission
 chmod 777 filename
To see the internal permission
 umask (max per. - umask = default permission)
 umask 000 (full permission for all)
 umask 777 (deny for all)
To change the owner of files or directory-
 chown <username> file/directory name
To change group of files & directory-
 chgrp <groupname> file/directory name

20. Commands for setting permission on a single user:
setfacl -m u:<user>:rwx /ww
It will set the full user permission on ww directory.
 getfacl <filename>
It will display full information about that file or directory.
Every user has its own UID (User Identification)
Every group has its own GID (Group Identification)
If UID matches (i.e. login user & owner) user permission is applicable.
If GID matches (i.e. login user & group) group permission is applicable.
If nothing matches other permission is applicable.

21. Files where UID & GID information saved:
/etc/passwd (UID)
/etc/shadow (UID in encrypted form)
/etc/group (GID)
/etc/gshadow (GID in encrypted form)