Understanding Hard Link and Soft Link in Linux
To understand the hard link and soft link you must first know What is an inode.
Everything in Linux is considered as a file.
An inode is a data structure that stores various information about a file in Linux, such as the access mode (read, write, execute permissions), ownership, file type, file size, group, number of links, etc. Each inode is identified by an integer number. An inode is assigned to a file when it is created.
A file system is divided into two parts – data blocks and inodes. The number of blocks is fixed once created, and can’t be changed. The name, path, location, links and other file attributes are not located in the directory. Directories are simply tables that contain the names of the files with the matching inode number.
To view, a file’s inode number use the below command
root@fundb:/HS# ls -li
total 10
865675319 -rwxrwxrwx 1 root root 1782 Aug 25 15:19 file_password_update.sh
865675318 -rwxrwxrwx 1 root root 365 Aug 25 15:19 tmpwatch
Hard Link and Soft Link
Hard Links
It is termed a mirror copy of the file.
Hard Links have the same inodes number.
ls -l command shows all the links with the link column showing the number of links.
Links have actual file contents
Removing any link, just reduces the link count but doesn't affect the other links.
You cannot create a Hard Link for a directory.
Even if the original file is removed, the link will still show you the contents of the file.
It works within the same filesystem.
It has the same inode number and permissions as the original file
Soft Links
It is the actual link to the file.
Soft Links have different inodes numbers.
ls -l command shows all links with second column value 1 and the link points to the original file.
Soft Link contains the path for the original file and not the contents.
Removing a soft link doesn't affect anything but when the original file is removed, the link becomes a 'dangling' link that points to a nonexistent file.
A Soft Link can link to a directory.
It can work between multiple filesystems.
It has a different inode number and file permissions than the original file
Example:
Let's say I have a file test
To create a soft link we use the below command.
ln -s test test_soft
How to remove
rm test_soft
or
unlink test_soft
To create a hard link we use the below command.
ln test test_hard
How to remove
rm test_hard
or
unlink test_hard
See the image below and compare what has been explained earlier.
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