How can we find all hard links to a given file? I.e., find all other hard links to the same file, given a hard link?
Does filesystem keep track of the hard links to a file?
The inode of a file only stores the number of hard links to the file, but not the hard links, right?
If the given file is called /path/to/file and you want to find all hard links to it that exist under the current directory, then use:
find . -samefile /path/to/file
The above was tested on GNU find. Although -samefile is not POSIX, it is also supported by Mac OSX find and FreeBSD find.
From GNU man find:
-samefile name
File refers to the same inode as name. When -L is in effect, this can include symbolic links.
ls -l lists the number of hard links to a file or directory. For directories, this number is larger than the number of results shown by find . -samefile. The reason for this is explained in the GNU find manual:
A directory normally has at least two hard links: the entry named in its parent directory, and the
.entry inside of the directory. If a directory has subdirectories, each of those also has a hard link called..to its parent directory.The
.and..directory entries are not normally searched unless they are mentioned on the find command line.
In sum, ls -l counts the . and .. directories as separate hard links but find . -samefile does not.
ls -al shows var/www/html/logs to have 4 links to it. I run find / -samefile /var/www/html/logs as user root and it shows me only one entry, not 4... what gives?
ls -al, every directory has a minimum of two links: itself and .. In addition, if it has subdirectories, then every subdirectory has a file .. that is a hard link back to its parent directory. Thus, according to ls -al, a directory with two subdirectories has a total of four hard links. By contrast, find / -samefile does not include the . and .. directories in its count.