Inodes (Index Nodes) store metadata for individual files and directories on the filesystem. Unlike superblocks, which contain information about the entire filesystem, inodes are responsible for individual files.
Key Information Stored in an Inode:
- File type: Indicates if the inode refers to a regular file, directory, symbolic link, etc.
- File permissions: Owner, group, and other permissions (read, write, execute).
- Owner (UID) and group (GID): User and group IDs associated with the file.
- File size: The size of the file in bytes.
- Timestamps: Includes the last access time, last modification time, and inode change time.
- Link count: The number of hard links pointing to the file.
- Pointers to data blocks: The inode contains pointers to the actual data blocks on disk that store the file contents.
- Direct pointers: Point directly to blocks.
- Indirect pointers: Can point to blocks that further point to other blocks, allowing larger files to be managed.
Inodes do not store the file name. Instead, filenames are stored in directories, which map the filenames to corresponding inode numbers.
Example:
When you create a new file, an inode is allocated for it. The inode will store all the file’s metadata (like permissions, size, etc.), while the actual file content is stored in disk blocks, and the inode contains pointers to those blocks.
Viewing Inode Information:
You can view information about a file’s inode with the ls command using the -i flag:
ls -i filename
This will show the inode number of the file.
To inspect the inode table:
stat filenamePractical Lab Exercise on Inodes:
Inode Information:
List the inode numbers of files in a directory:
ls -i /path/to/directory
View detailed inode information of a specific file:
stat /path/to/file
Summary of Superblock vs Inode:
| Aspect | Superblock | Inode |
|---|---|---|
| Scope | Describes the entire filesystem | Describes individual files and directories |
| Purpose | Stores global filesystem metadata | Stores metadata specific to a file or directory |
| Information | Filesystem size, block size, free blocks, inodes, etc. | File permissions, ownership, timestamps, pointers to data |
| Location | Stored at specific locations on disk (with backups) | Inodes are scattered throughout the filesystem |
| Contains | Filesystem-wide information | File-specific information (but not the filename) |