Inode(Index Node)

• Inode is a date structure.
• It stores the metadata and other information of files except the file name.
• Each file and Directory has its own unique inode.

Type of Info stored in Inode

Metadata

• File type
• File permissions
• Owner and Group ID(UID & GID)
• File size
• Timestamps (birth, access, modification, change times)
• Number of Hard link & Soft Link (Symbolic Link)

Location of Data blocks

Pointers of the disk blocks where data is stored.

the file name and the directory path is not stored in inode these info are managed separately in [[Directory Entry]] that map file names to inode numbers.

Working of Inode

• Each file and directory has its inode.
• When new file or directory is created the file-system assigns a unused inode to it.
• It serves as identifier for file and directory.

Viewing Inode

ls -i

Creation of inodes

• When a file system is created a fixed number of inodes are pre-allocated based on the size of file-system.
• The number of inodes are in the ratio with the file system size. (like 1 inode per 16KB).

Dynamic assignment of inodes

• When new file or directory is created the file-system looks for first available unallocated inode from the inode table and assign it.
• inode number can be reused, when file or directories are deleted the inode of those are marked unallocated by the file-system and then can be reused.