Linux Classroom Series – 07/Aug/2020

Linux file systems

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

Basic concepts in File Systems

Preview

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) Preview

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 Preview

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

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