1. Getting Started with Linux
Session #1

2. UNIX History

3. UNIX Concepts UNIX Structure Some Basic Commands UNIX File System
Files: permissions, properties, manipulation
Principal Linux Files

4. Topics

5. Some Basic Commands
who, who am i
date
echo

6. UNIX Files and File System

7. UNIX File Tree

8. Debian Directory Tree

9. User File Tree

10. File System Usage Directories: examples Absolute and relative paths
Where I am? - pwd
Moving around: cd command ()
Creating and removing: mkdir, rmdir, rm -r
examples

11. File System Layout

12. The ext2 superblock Magic Number Revision Level
This allows the mounting software to check that this is indeed the Superblock for an EXT2 file system. For the current version of EXT2 this is 0xEF53.
Revision Level
The major and minor revision levels allow the mounting code to determine whether or not this file system supports features that are only available in particular revisions of the file system. There are also feature compatibility fields which help the mounting code to determine which new features can safely be used on this file system,
Mount Count and Maximum Mount Count
Together these allow the system to determine if the file system should be fully checked. The mount count is incremented each time the file system is mounted and when it equals the maximum mount count the warning message ``maximal mount count reached, running e2fsck is recommended'' is displayed,
Block Group Number
The Block Group number that holds this copy of the Superblock,
Block Size
The size of the block for this file system in bytes, for example 1024 bytes,
Blocks per Group
The number of blocks in a group. Like the block size this is fixed when the file system is created,
Free Blocks
The number of free blocks in the file system,
Free Inodes
The number of free Inodes in the file system,
First Inode
This is the inode number of the first inode in the file system. The first inode in an EXT2 root file system would be the directory entry for the '/' directory.

13. Directory
inode The inode for this directory entry. This is an index into the array of inodes held in the Inode Table of the Block Group
name length The length of this directory entry in bytes,
name The name of this directory entry.

14. Attributes and Manipulation
Files
Attributes and Manipulation

15. Simple file commands
Simple File Commands
List the files and directories in the working (current) directory ls
Display the contents of the file File1 concatenated with the contents of the file File2
cat File1 File2
Change the name of (move) file File1 to File3
mv File1 File3
Make a copy of File1 and call it File3
cp File1 File3
Erase (remove) the file File4
rm File4
Display the contents of File1 a page at a time, q to stop displaying
less File1
Print the contents of File1 on the default printer
lpr File1

16. File Types Everything is a file! Removed by Created by Symbol Type rm
cp, editors, etc. -
regular
rmdir, rm -r
mkdir d
Directory
mknod b
block device file c
Character device file p
Named pipe
ln -s l
Symbolic link
socket s
Unix Domain Socket

17. File Permissions x w r d Other Group Owner Execute Write Read
Execute
Write
Read
Directory
Examples:
drwxr-xr-x
A folder which has read, write and execute permissions for the owner, but only read and execute permissions for the group and for other users.
-rw-rw-rw-
A file that can be read and written by anyone, but not executed at all.
-rw-r--r--
A file that can be read and written by the user, but only read by the group and everyone else

18. Numerical File Permissions Notation
Execute (X)
Write )W(
Read (R)
Number No
Yes 1 2 3 4 5 6 7
Examples:
777 is the same as rwxrwxrwx
755 is the same as rwxr-xr-x
666 is the same as rw-rw-rw-
744 is the same as rwxr--r--

19. Displaying File Information

20. I-node

21. directory examples cd /usr/local/bin cd .. pwd
cd (go to home directory)
mkdir //tmp/mydir
rmdir /tmp/mydir
mkdir /tmp/mydir; cd /tmp/mydir; mkdir one_more_dir
rmdir one_more_dir What happens?
rm –r one_more_dir

22. Principal Linux Files Description File Linux kernel /boot/vmlinuz*
Filesystems mounted or available for mounting
/etc/fstab
Map of IP numbers to hostnames
/etc/hosts
Hosts allowed to access Internet services
/etc/hosts.allow
Hosts forbidden to access Internet services
/etc/hosts.deny
Configuration for the inetd daemon, which controls access to Internet services
/etc/inetd.conf
Configuration for the init daemon, which controls executing processes
/etc/inittab
Linux kernel and distribution version
/etc/issue
User account information
/etc/passwd
Secure user account information
/etc/shadow
Grub loader configuration file
/boot/grub/menu.lst
Default environment for users of BASH shell
/etc/profile
Scripts for system and process startup and shutdown
/etc/rc*.d
Scripts for system boot
/etc/rc.boot
System log
/var/log/messages