Linux File System

1. Linux File System 1

2. Contents • What is File System? • Important Directories in Linux • Mounting File System • Partitions • Creating File System • Some useful commands and tools 2

3. What is File System? • It is responsible for storing information on disk and retrieving and updating this information. • Example : • FAT16, FAT32, NTFS • ext2, ext3 • … • In Linux everything is file. 3

4. Type of File System • Network File System • NFS • SMB • Disk File System • ext2 • ext3 • FAT32 • NTFS 4

5. Network File System • Network File System are physically somewhere else, but appear as if they are mounted on one computer. • NFS • It was developed by Sun. • SMB • It was developed by Microsoft. 5

6. Disk File System • Disk File System are what you will find on a physical device, such as hard drive in a computer. 6

7. ext2 File System • It has been the standard File System for Linux. • The original Extended File System was named ext. • The ext2 File System can accommodate: • Files as large as 2GB • Directories as large as 2TB • Max. file name length of 255 characters. 7

8. ext2 Structure • A file in the ext2 File System begins with the inode. • inode • Each file has an inode structure that is identified by an i-number. • The inode contains the information required to access the file. • It doesn’t contain file name. • Inodes store information on files, such as • user and group ownership, • access mode (read, write, execute permissions) • and type of file. 10

9. ext3 File System • It is as same as ext2. • It is a journaling File System for Linux. • In a journaling system, metadata is written to a journal on the disk before it is actually used to modify the file. 13

10. Contents • What is File System? • Important Directories in Linux • Mounting File System • Partitions • Creating File System • Some useful commands and tools 14

11. File System Structure / /bin /etc /dev … /usr /home /root ls ping /A /B data.txt pic.gif 15

12. The Root Directory • /mnt • /opt • /proc • /root • /sbin • /usr • /srv • /tmp • /var • /bin • /boot • /dev • /etc • /home • /initrd • /lib • /lost+found • /media 16

13. /bin • Hold the most commonly used essential user programs • login • Shells (bash, ksh, csh) • File manipulation utilities (cp, mv, rm, ln, tar) • Editors (ed, vi) • File system utilities (dd, df, mount, umount, sync) • System utilities (uname, hostname, arch) • GNU utilities like gzip and gunzip 17

14. /bin detail • cat • chgrp • chmod • chown • cp • date • dd • df • dmesg • echo • false • Utility to concatenate files to standard output • Utility to change file group ownership • Utility to change file access permissions • Utility to change file owner and group • Utility to copy files and directories • Utility to print or set the system data and time • Utility to convert and copy a file • Utility to report filesystem disk space usage • Utility to print or control the kernel message buffer • Utility to display a line of text • Utility to do nothing, unsuccessfully 18

15. /bin detail (cont) • hostname • kill • ln • login • ls • mkdir • mknod • more • mount • mv • ps • Utility to show or set the system's host name • Utility to send signals to processes • Utility to make links between files • Utility to begin a session on the system • Utility to list directory contents • Utility to make directories • Utility to make block or character special files • Utility to page through text • Utility to mount a filesystem • Utility to move/rename files • Utility to report process status 19

16. 1. /bin detail (cont) • pwd • rm • rmdir • sed • sh • stty • su • sync • true • umount • uname • Utility to print name of current working directory • Utility to remove files or directories • Utility to remove empty directories • The `sed' stream editor • The Bourne command shell • Utility to change and print terminal line settings • Utility to change user ID • Utility to flush filesystem buffers • Utility to do nothing, successfully • Utility to unmount file systems • Utility to print system information 20

17. /sbin • Hold essential maintenance or system programs such as the following: • fsck • Fdisk • Mkfs • Shutdown • Lilo • Init • … • The main difference between the programs stored in /bin and /sbin is that the programs in /sbin are executable only by root. 21

18. /sbin … detail • shutdown • Fastboot • Fasthalt • fdisk • fsck • fsck.* • getty • halt • ifconfig • Command to bring the system down. • Reboot the system without checking the disks (optional) • Stop the system without checking the disks (optional) • Partition table manipulator (optional) • File system check and repair utility (optional) • File system check and repair utility for a specific filesystem (optional) • The getty program (optional) • Command to stop the system (optional) • Configure a network interface (optional) 22

19. /sbin … detail • init • mkfs • mkfs.* • mkswap • reboot • route • swapon • swapoff • update • Initial process (optional) • Command to build a filesystem (optional) • Command to build a specific filesystem (optional) • Command to set up a swap area (optional) • Command to reboot the system (optional) • IP routing table utility (optional) • Enable paging and swapping (optional) • Disable paging and swapping (optional) • Daemon to periodically flush filesystem buffers (optional) 23

20. /etc • Store the systemwide configuration files required by many programs. • passwd • shadow • fstab • hosts • lilo.conf • … 24

21. /etc … detail • /etc/X11/ : contains all the configuration files for the X Window System • /etc/X11/XF86Config, /etc/X11/XF86Config-4 : 'X' configuration file • /etc/ftpchroot : List of ftp users that need to be chrooted • /etc/ftpaccess : Determines who might get ftp-access to your machine. • /etc/gateways : Lists gateways for 'routed' • /etc/group, /etc/passwd. lists the configured user groups and who belongs to them. • /etc/hostname : Contains the hostname of your machine • /etc/host.conf : Determines the search order for look-ups 25

22. /home and /root • The /home directory is where all the home directories for all the users on a system are stored. • The /root directory is where all the home directories for root user on a system are stored. 27

23. /dev • The special files representing hardware are kept in it. • /dev/hda1 • /dev/ttyS0 • /dev/mouse • /dev/fd0 • … 28

24. /dev … detail • /dev/ttyS0 • /dev/psaux • /dev/lp0 • /dev/dsp • /dev/usb • /dev/sda • /dev/scd • /dev/cdrom • /dev/fd0 • /dev/hda • Device connected to Com1 (Modem, mouse,..) • PS/2 mouse connection • First parallel port • Sound card (Digital Signal Processor) • USB device nodes. • First SCSI device • First SCSI CD-ROM device • CD-ROM drive • floppy drive • The partition on primary hdd 29

25. /tmp and /var • The /tmp and /var directories are used to hold temporary files with constantly varying content. 30

26. /usr • Most programs and files directly relating to users of the system are stored. • It is in some ways a mini version of the / directory. • /usr/bin • /usr/sbin • /usr/spool • … 31

27. /proc • It is a virtual File System • A special File System provided by the kernel as a way of providing information about the system to user programs. • The main tasks of proc File System is to provide information about the kernel and processes. • runtime system information (e.g. system memory, devices mounted, hardware configuration, etc). 32

28. Other directories • /mnt • removable media such as CD-ROM, floppy and … are mounted. • /mnt/floppy • /mnt/cdrom • /boot • Image to boot system • /lost+found 33

29. /boot … detail • /boot/boot.0300 • /boot/boot.b • /boot/chain.b • /boot/config-kernel-version • /boot/map • /boot/vmlinuz • /boot/vmlinuz-kernel-version • … • Backup master boot record. • The basic boot sector • Used to boot non-Linux operating systems • Installed kernel configuration. A config line such as: CONFIG_FONT_8x8=y • The location of the kernel • Normally the kernel or symbolic link to the kernel 34

30. /lost+found • Contains the files which were recovered after an unexpected event, such as a proper shutdown. • Try to move each file back to its original location 37

31. /media • Contains subdirectories which are used as mount points for removeable media • such as floppy disks, cdroms and zip disks 38

32. /mnt • This is a generic mount point under mounted • (mount is to make a filesystem available to the system) the filesystems or devices. • When a filesystem no longer needs to be mounted, it can be unmounted with umount • mount /dev/hda2 /home • umount /dev/hda2 39

33. /opt • This directory is reserved for all the software and add-on packages that are not part of the default installation • /opt/'package'  C:\Windows\Progam Files\"Program Name" 40

34. Contents • What is File System? • Important Directories in Linux • Mounting File System • Partitions • Creating File System • Some useful commands and tools 41

35. Mounting File System • The Linux File System makes it appear as if all the File System are local and mounted somewhere on the root File System. • File System are mounted with the mount command. • mount –t type source mount_point • To unmount a File System, the umount command is used. • umount /dev/<device name> or mount_point 42

36. Mounting Automatically with fstab • This file lists all the partitions that need to be mounted at boot time and the directory where they need to be mounted. • Along with that information, you can pass parameters to the mount command. • /etc/fstab • Which devices to be mounted • What kinds of File Systems they contain • At what point in the File System the mount takes place • … 43

37. fstab Example 44

38. fstab Structure • Each line has six fields: • 1’st field: indicates the block device or remote File System that will be mounted. • 2’nd field: identifies the mount point the local system where the File System will be mounted. • 3’rd field: File System type • 4’th field: list of mount options • 5’th field: it is used by dump (a backup program) to determine whether the File System should be dumped (1:yes, 0:no). • 6’th field: it is used by fsck (0:never run, 1:run on the drive at predetermined, 2:it is recommended for non root File System so that fsck isn’t run on them as frequently). 45

39. Contents • What is File System? • Important Directories in Linux • Mounting File System • Partitions • Creating File System • Some useful command and tool 46

40. Partition Table • MBR (Master Boot Record) • The first sector • 512 bytes (446 bytes:boot loader such as LILO or GRUB, 64bytes:partition table, 2 bytes:special code). • The partition table has enough room for four partitions. • One of the four can be used as an extended partition. 47

41. Partitions • Primary-Master • /dev/hda • Primary-Slave • /dev/hdb • Secondary-Master • /dev/hdc • Secondary-Slave • /dev/hdd • Swap Partition • Used to implement virtual memory 48

42. fdisk • The Linux fdisk counterpart in DOS edits the disk structure. • You must be the superuser (root) to run fdisk. • You can run command fdisk -l to display list of partitions • fdisk /dev/had • cfisk • It is the same as fdisk, but it gives a graphical interface at the console. 49

43. fdisk Command 50

44. Contents • What is File System? • Important Directories in Linux • Mounting File System • Partitions • Creating File System • Some useful commands and tools 51

45. Creating File System • Once a disk has been partitioned for a specific File System, it is necessary to create a File System on it. • The first process in the DOS world is known as formatting. • In the UNIX world is known as creating a File System. 52

46. Create File System Commands • mkfs or mke2fs • Make a new ext2 File System. • mk3fs • Make a new ext3 File System. • mkdosfs • Make DOS File System without owning any Microsoft software. 53

47. Formatting Linux Filesystem • Step #1 Create the new filesystem with following command (first login in as a root user) • mkfs.ext3 /dev/sda5 • Step # 2: Create mount point directory for the file system • # mkdir /datadisk1 • Step # 3: Mount the new file system • # mount /dev/sda5 /datadisk1 • Step # 4: Finally make sure file system /dev/hda5 automatically mounted at /datadisk1 mount point after system reboots. • vi /etc/fstab • Add/append following entry to file: • /dev/sda5 /datadisk1 ext3 defaults 0 2 54