[LINUX] What is the difference between a symbolic link and a hard link?

Do you know the difference between symbolic links and hard links and how to use them properly? I didn't know much about it, so I searched for related articles.

This article was intuitively easy to understand as a figure. Each feature is also written in an easy-to-understand manner. https://eng-entrance.com/linux-permission-link

Symbolic link

Isn't it easy to understand the image of symbolic links as shortcuts? Consider creating a symbolic link symkink_fname that references a file called ʻoriginal_fname`.

./original_fname ./symlink_fname


cat ./symlink_fname

When you run

cat ./original_fname

Should mean the same operation as. In other words

rm ./symlink_fname


rm ./original_fname

Will be equivalent to, and the original file ʻoriginal_fname` will be deleted.

Regarding this, the precautions when deleting symbolic links are described in this article, for example. https://mimirswell.ggnet.co.jp/blog-165 The point is that you can delete the link with the rm command, but it's dangerous, so let's use ʻunlink`.

Hard link

On the other hand, what about hard links?

./original_fname ./hardlink_fname

Each path will point to the same entity file. In this state

open ./hardkink_fname

When you execute

open <Entity file>

It means. What's interesting is that there's something like a reference counter to a real file,

rm ./hardkink_fname

Will delete the path ./hardkink_fname, but not the actual file.

Because, originally, the situation I'm thinking about now ./original_fname ./hardlink_fname Because there were two "references" in, even if one "reference" is deleted, one still remains.

And when the number of "references" becomes 0, the entity seems to be deleted.

inode and entity file

Until now, we have used the words "entity" and "reference" to grasp the image, but to explain it properly, we need to touch the inode.

Is this article easy to understand? https://qiita.com/katsuo5/items/fc57eaa9330d318ee342

How to use hard links

It seems that symbolic links are commonly used. So when are hard links used?

Read the answer to this question, I see! I think. https://q.hatena.ne.jp/1265361495

It is said that the destination is used to refer to the mail of multiple people on the IMAP server. It means that you don't have to copy it and it will be deleted properly.

...I learned a lot!

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