Where are filenames stored on a filesystem?

Question

It's not in inode or with the actual file content since we have hard link that two filenames can point to the same inode.

Strictly speaking, that depends entirely on which filesystem you are talking about. Not all of them have inodes (or even directories). — Michael Borgwardt, Feb 28 '14 at 14:26
NTFS or FAT12/16/32 and many other filesystems don't have any inode — phuclv, Feb 28 '14 at 15:10
Many files have more than a name in more than one directories. All files of type directory have at least 2 names, one of them being . in themselves. — Stéphane Chazelas, Mar 31 '14 at 20:58
@LưuVĩnhPhúc, ntfs does.. it just calls it an MFT record, but it's pretty much an inode. — psusi, Apr 01 '14 at 01:10

score 73 · Accepted Answer · edited Mar 20 '17 at 10:04

I wasn't finding a suitable duplicate so here's an answer to your question.

File names & directories

excerpt

File names and directory implications:

inodes do not contain file names, only other file metadata.

Unix directories are lists of association structures, each of which contains one filename and one inode number.

The file system driver must search a directory looking for a particular filename and then convert the filename to the correct corresponding inode number.

Source: Wikipedia page on Inode

So the name of the file is stored within the directories' information structure. For example:

ss of fs

Directory's structure

excerpt

In the EXT2 file system, directories are special files that are used to create and hold access paths to the files in the file system. Figure 9.3 shows the layout of a directory entry in memory.

A directory file is a list of directory entries, each one containing the following information:

inode - The inode for this directory entry. This is an index into the array of inodes held in the Inode Table of the Block Group. In figure 9.3, the directory entry for the file called file has a reference to inode number i1,

name length - The length of this directory entry in bytes,

name - The name of this directory entry.

The first two entries for every directory are always the standard . and .. entries meaning "this directory" and "the parent directory" respectively.

Here's the Figure 9.3 references above:

ss #2

Source: The Linux Documentation Project: Filesystem

References

Hauke Laging · Answer 2 · 2014-03-31T22:47:03.377

9

The file name is stored in the respective directory ("directory file"). This entry points to an inode.

edited Mar 31 '14 at 22:47

answered Feb 27 '14 at 20:45

Hauke Laging

90,279

1

I can't see how symlink targets could end-up in directory entries. The symlink target may be found in the symlink's inode, but not in (any of) the directory entry that symlink is linked to, that would not make sense. – Stéphane Chazelas Mar 31 '14 at 20:57
1

@StéphaneChazelas, the symlink itself simply contains another name that should be opened instead. The name lookup starts again on the new name, which ( if it exists at all ) is a directory entry somewhere. – psusi Jun 03 '15 at 01:50

score 5 · Answer 3 · edited Jul 08 '22 at 07:13

5

Filenames are stored in the directory data structures, which have the filename (a string) and the corresponding inode number.

directory is responsible for mapping filename --> inode.

and inode is responsible for mapping data area location --> sector on disk.

edited Jul 08 '22 at 07:13

ilkkachu

138,973

answered Apr 05 '15 at 08:47

JustVirtually

51

Where are filenames stored on a filesystem?

3 Answers3

File names & directories

Directory's structure

References

Linked

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