俗话说，一幅画胜过千言万语。以下是我对它的想象:

下面是我们如何得到这张照片的:

Create a name myfile.txt in the file system that points to a new inode (which contains the metadata for the file and points to the blocks of data that contain its contents, i.e. the text "Hello, World!": $ echo 'Hello, World!' > myfile.txt Create a hard link my-hard-link to the file myfile.txt, which means "create a file that should point to the same inode that myfile.txt points to": $ ln myfile.txt my-hard-link Create a soft link my-soft-link to the file myfile.txt, which means "create a file that should point to the file myfile.txt": $ ln -s myfile.txt my-soft-link

看看如果myfile.txt被删除(或移动)会发生什么:my-hard-link仍然指向相同的内容，因此不受影响，而my-soft-link现在什么都不指向。其他答案讨论了每种方法的利与弊。

当原始文件被移动时，硬链接非常有用。例如，将文件从/bin移动到/usr/bin或/usr/local/bin。到/bin中文件的任何符号链接都将被破坏，但是硬链接(直接到文件的inode的链接)不会关心。

硬链接可能占用更少的磁盘空间，因为它们只占用一个目录条目，而符号链接需要自己的inode来存储它所指向的名称。

Hard links also take less time to resolve - symlinks can point to other symlinks that are in symlinked directories. And some of these could be on NFS or other high-latency file systems, and so could result in network traffic to resolve. Hard links, being always on the same file system, are always resolved in a single look-up, and never involve network latency (if it's a hardlink on an NFS filesystem, the NFS server would do the resolution, and it would be invisible to the client system). Sometimes this is important. Not for me, but I can imagine high-performance systems where this might be important.

I also think things like mmap(2) and even open(2) use the same functionality as hardlinks to keep a file's inode active so that even if the file gets unlink(2)ed, the inode remains to allow the process continued access, and only once the process closes it does the file really go away. This allows for much safer temporary files (if you can get the open and unlink to happen atomically, which there may be a POSIX API for that I'm not remembering, then you really have a safe temporary file) where you can read/write your data without anyone being able to access it. Well, that was true before /proc gave everyone the ability to look at your file descriptors, but that's another story.

说到这里，恢复一个在进程a中打开，但在文件系统中未链接的文件需要使用硬链接来重新创建inode链接，这样当打开该文件的进程关闭或离开时，该文件不会消失。

俗话说，一幅画胜过千言万语。以下是我对它的想象:

下面是我们如何得到这张照片的:

Create a name myfile.txt in the file system that points to a new inode (which contains the metadata for the file and points to the blocks of data that contain its contents, i.e. the text "Hello, World!": $ echo 'Hello, World!' > myfile.txt Create a hard link my-hard-link to the file myfile.txt, which means "create a file that should point to the same inode that myfile.txt points to": $ ln myfile.txt my-hard-link Create a soft link my-soft-link to the file myfile.txt, which means "create a file that should point to the file myfile.txt": $ ln -s myfile.txt my-soft-link

看看如果myfile.txt被删除(或移动)会发生什么:my-hard-link仍然指向相同的内容，因此不受影响，而my-soft-link现在什么都不指向。其他答案讨论了每种方法的利与弊。

What you think of as an ordinary "file" is actually two separate things: The data of a file, and a directory entry. When you create a hard link for a file, you actually create a second directory entry which refers to the same data. Both directory entries have the exact same functionality; each one can be used to open the file to read it. So you don't really have "a file plus a hard link", you have "file data with two directory entries". What you think of as deleting a file actually deletes a directory entry, and when the last directory entry for the data is deleted, then the data itself is deleted as well. For ordinary files that have only one directory entry, deleting the directory entry will delete the data as always. (While a file is opened, the OS creates a temporary link to the file, so even when you delete all directory entries, the data stays but disappears as soon as you close the file).

例如，创建文件a .txt，硬链接B.txt，然后删除a .txt。当您创建a .txt时，会创建一些数据，并创建一个目录条目a .txt。在创建硬链接时，创建了另一个目录条目B.txt，指向完全相同的数据。当您删除a .txt时，您仍然拥有所有数据和一个目录条目B.txt，就像您首先创建了一个文件B.txt一样。

软链接只是一个(几乎)普通的文件，只是它不包含数据，而是另一个目录条目的路径。如果你删除了软链接所指向的文件，那么软链接将包含一个不再指向目录条目的路径;它坏了。如果你删除软链接，就像删除任何其他文件一样，它指向的文件不受影响。

在这个答案中，当我说文件时，我指的是内存中的位置

所有保存的数据都使用称为inode的数据结构存储在内存中，每个inode都有一个inodennumber。inode号用于访问inode。到文件的所有硬链接可能有不同的名称，但共享相同的inode号。因为所有的硬链接都有相同的inodennumber(访问相同的inode)，所以它们都指向相同的物理内存。

符号链接是一种特殊的文件。因为它也是一个文件，它将有一个文件名和一个inode号。如上所述，inode号访问指向数据的inode。现在，符号链接的特殊之处在于，符号链接中的inodennumbers访问那些指向另一个文件的“路径”的inode。更具体地说，符号链接中的inode号访问指向另一个硬链接的inode。

当我们在GUI中移动、复制、删除文件时，我们使用的是文件的硬链接，而不是物理内存。当我们删除一个文件时，我们正在删除该文件的硬链接。我们并没有清除物理内存。如果文件的所有硬链接都被删除，那么将无法访问存储的数据，尽管它可能仍然存在于内存中

我刚刚发现了一个简单的方法来理解硬链接在一个常见的场景，软件安装。

有一天，我下载了一个软件到下载文件夹进行安装。在我做sudo make install后，一些可执行文件被cped到本地bin文件夹。这里，cp创建硬链接。我对这个软件很满意，但很快就意识到，从长远来看，下载并不是一个好地方。所以我把软件文件夹移动到源目录。好吧，我仍然可以像以前一样运行软件而不用担心任何目标链接的事情，就像在Windows中一样。这意味着硬链接可以直接找到inode和其他文件。