Linux file systems

• File systems provides a means of organizing data on storage devices.

Basic concepts in File Systems

i-Nodes

• Inode is a data structure and it defines file or a directory on the filesystem
• Inodes point to blocks that makeup a file
• The control information in the i-node includes
  • file owner
  • time of last acess
  • creation time
  • group Id
• Each directory gets an i-node & inode points to the datablocks containing information (filenames & i-nodes)

Block

• Data on ext* file system is organized into block, A block is sequence of bytes.
• Each block smallest addressable unit in storage device
• Blocks are in turn grouped into block groups & each block group consists of superblock.
• Superblock is first piece of information read from disk, This small datastructure reveals information such as
  • available space
  • location of i-node

Filesystems in linux

• The popular filesystems in linux are
  • ext4:
    • Supports maximum file system size of 1EB (exabyte)
    • Supports maximum individual file sizes up to 16TB each.
  • XFS
    • Journal base 64 bit file system.
    • Supports files systems as large as 8EiB (Exbibytes == 8 million terrabytes)
    • Supports maximum individual file sizes up to 8EiB (Exbibytes == 8 million terrabytes)
  • Btrfs:
    • Next generation Linux file system. In addition to all the features of ext4, Btrfs supports
      • Dynamic i-node allocation and transparent compressing
      • Online file system checking
      • Buit-in RAID functions such as mirroring & stripping

Commands useful for storage

• Disk Utilization:
  • The du command allows you to determine disk utilization on a directory-by-directory basis
  • For du examples Refer Here
  • To display total amount of space used by all the files & directories in PWD

  du -sh .
  

• Disk free:
  • The df program displays the amount of free space available on the mounted file system.
  • To show free space for all locally mounted drives use this command

  sudo df -l
  

  • To show the free space in human-readable format

  sudo df -h
  

Next steps

• Mounting & un mounting in linux
• Making file systems
• Partitions using LVM (Logical Volume Manager)

Exercise:

• Please find out about a tool called as rsync