What is an inode in a Linux server and why you need to know!

InodesFor those of you who have been in the web hosting industry for any length of time, I’m sure you’ve seen the inode limits some providers impose on their web hosting plans. If you exceed those limits, well it isn’t pretty. To the day in and day out Internet user, inode is a term not widely recognized.

Inodes can be thought of as a database of information

In Linux servers, inodes are filesystem objects, sometimes called index nodes or i-nodes. You can think of inodes as a file structure, or possibly a database of all the information on a server, other than file names themselves or the contents of actual files. What this database does is identify the owners of the files, their permissions and miscellaneous metadata. Essentially, every image, file, email, directory and symbolic link on your Linux server requires an inode.

What cPanel recommends for allotments of inodes

Inodes are allocated on cPanel, which recommends actually setting up more than the default allocation of inodes on your Linux server’s partitions. Typically, an allocation of inodes is assigned when the file system of a server is created, and that usually accounts for 1% of total size.

cPanel goes on to recommend if everything is installed on just one partition, that the base WHM & cPanel requires at minimum one million inodes, plus at minimum fifty thousand inodes per cPanel account used for hosting.

How are inodes structured?

A table of inodes is located on a specific section of the server whereby an inode number can then index that. You can find a file’s inode number by using the ls -i command. Files that are stored on the HDD can be tracked via inodes which store metadata that points to files, directories or objects. Of the 128 bytes used in each metadata entry, certain attributes are included such as the inode number, ACL, file size, number of blocks, file access time, owner, permissions, file deletion time and status flags, among others. What metadata does not include are the file names themselves.

What happens when the inode structure is full?

It is possible to fill an inode structure before the space on the hard drive is filled. Why? The inode structure is limited in size, so if the drive contains lots and lots of small files, each taking up 128 bytes of the inode structure, you won’t be able to create more files on the disk. The workaround is simply to free up inode storage.

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Steve

Director of Sales and New Business Development at ProlimeHost
Steve's been in the web hosting industry since 1997, helping clients optimize their online solutions from shared hosting and colocation to VPS and dedicated servers.

ProlimeHost specializes in dedicated servers, with data centers in Los Angeles, Utah and Denver. Call +1 877 477 9454 or email us at Sales@ProlimeHost.com. We’re here to help.
Steve

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