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An Inode specifies which DiskClusters a file occupies as well as a few attributes such as creation and last-modification times. To that end it contains a list of direct, indirect, and doubly and triply indirect pointers. On some FileSystems, very small files can be stored directly in the Inode itself.

Sophisticated FileSystems create Inodes on demand, but with most, the number of Inodes on a Partition has to be decided on during FileSystem creation. It is rare to run out of Inodes unless you have an unusual usage profile such as storing a news spool or Squid cache. Exhaustion of the inodes will prohibit the creation of additional files even if sufficient HDD space exists.

How many Inodes do I have free?

  • df - i

What information does an Inode store?

  • The size of the file in bytes.
  • The file's physical location (the addresses of the blocks of storage containing the file's data on a HDD)
  • The file's access permissions
  • Timestamps (ctime,mtime and atime). See FileTimes?
  • A reference count telling how many hard links point to the Inode.

How to obtain a file's Inode number

  • ls -i <file>