{"id":1233,"date":"2010-09-28T12:13:58","date_gmt":"2010-09-28T05:13:58","guid":{"rendered":"http:\/\/www.jfdesignnet.com\/?p=1233"},"modified":"2010-09-28T12:13:58","modified_gmt":"2010-09-28T05:13:58","slug":"softlinks-vs-hardlinks","status":"publish","type":"post","link":"https:\/\/www.jfdesignnet.com\/?p=1233","title":{"rendered":"Softlinks vs Hardlinks"},"content":{"rendered":"

Many times I have to explain this two kind of file links in linux, softlinks<\/strong> and hardlinks<\/strong> over and over again, and I realized it is something many people might be unfamiliar with, especially users migration from Winblows. I think it would be nice if I explain this here and just give the link for those who need. Here, I\u2019ll give a quick explanation of what these types of links are, and when you should use them.<\/p>\n

What is Softlink ?<\/strong><\/span><\/p>\n

Softlinks are the easiest to understand, especially because you\u2019ve probably already used them. A softlink fills the same role as a Winblows shortcut. Simply put, a softlink is a file that points to another file. When you create a softlink, you are creating a new file that exists only as a pointer to a file elsewhere on the system.<\/p>\n

All links are created with the ln<\/code> command, using the -s<\/code> flag if you want a softlink (if you don\u2019t use -s<\/code>, you\u2019ll get a hardlink, which I\u2019ll talk about in a second). The syntax of the command is :<\/p>\n

{code}ln -s [target] [link name]{\/code}<\/p>\n

For example, the following command will create a softlink to \/usr\/bin\/dolphin called dolphin (in my \u201cDesktop\u201d directory) :<\/p>\n

{code}ln -s \/usr\/bin\/dolphin ~\/Desktop\/dolphin{\/code}<\/p>\n

You can see the softlink\u2019s target by using the ls -l<\/code> command. You can also use this command to detect broken softlinks :<\/p>\n

\"\"<\/a>
\nNow that we understand softlinks, let\u2019s talk about hardlinks.<\/p>\n

What is Hardlink ?<\/strong><\/span><\/p>\n

Whereas a softlink is a new file that points to an already-existing file, a hardlink is another instance of the original file<\/em>. A diagram is the easiest way to explain what that means :<\/p>\n

\"\"<\/a>\"\"<\/a><\/p>\n

\n

You can click on either of the images for a larger version. What it explains is that, when you create a hardlink, you are creating another pointer to the data location on disk, not a pointer to the existing file. That means that editing a hard link of a file is equivalent to editing the original instance of the file.<\/p>\n

To drive the point home: a softlink is a shortcut to an existing file, whereas a hardlink is a reference to a location on disk (or, more accurately, a location in the filesystem). This means that the concept of a shortcut, a link pointing to another file, doesn\u2019t make sense for hardlinks. But, what does make sense is asking how many references exist to a given location on disk (how many hardlinks exist for a file), which you can see by running the \u2018stat\u2019 command :<\/p>\n

{code}stat \/path\/to\/file{\/code}<\/p>\n

So for example, in this screenshot I\u2019ve created a file and then built three hardlinks to it. When I run the \u2018stat\u2019 command on any of the files, it will show that there is a reference count of 4 :<\/p>\n

\"\"<\/a>I think you now understand what the hardlink is.<\/p>\n

When to use Softlink ?<\/strong><\/span><\/p>\n

There are two major limitations of hardlinks. In these cases, you must<\/em> use a softlink :<\/p>\n

A link across filesystems<\/strong>
\nBecause a hardlink is a direct reference to the underlying filesystem, you can\u2019t hardlink across filesystems.<\/p>\n

Linking to a directory<\/strong>
\nYou can\u2019t use a hardlink to link to a directory.<\/p>\n

In the cases listed above, you must<\/em> use a softlink because a hardlink simply won\u2019t work. There are also cases where softlinks are preferable to hardlinks, even though either will work. For example, you\u2019d probably want to pick a softlink when you want to create a shortcut<\/em> especially when the destination of that shortcut might change in the future. For example, if you have a launcher to a beta version of an application, you may wish to use a softlink so you can easily change the target of the link between versions.<\/p>\n

In most of the remaining cases (creating a link to a file on the same filesystem), hardlinks can be preferable for the following major reasons :<\/p>\n

1. Performance<\/strong><\/p>\n

There is a slight performance boost to be gained from using hardlinks. This is because since a hardlink references a spot on disk, rather than referencing another another file (which then references the actual spot on disk you want), there is one less disk seek involved in hardlinking.<\/p>\n

2. Storage space<\/strong><\/p>\n

Hardlinks don\u2019t take up any additional space, since they are simply a reference to an already existing space of disk. Creating a softlink is creating a new file, and will consume a small amount (usually 4KB) of space on your filesystem.<\/p>\n

Additionally, hardlinks are preferable because a softlink is vulnerable to losing the \u2018master\u2019 instance of a file (the file to which all the softlinks point). If the original file is deleted, then all softlinks to it become invalid. With a hardlink, you can delete any of the instances, including the original, and as long as at least one instance exists the file will remain on the system.<\/p>\n

I hope this information was helpful and easy to understand.<\/p>\n","protected":false},"excerpt":{"rendered":"

Many times I have to explain this two kind of file links in linux, softlinks and hardlinks over and over again, and I realized it is something many people might be unfamiliar with, especially users migration from Winblows. I think it would be nice if I explain this here and just give the link for […]<\/p>\n","protected":false},"author":1,"featured_media":1238,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[110,224],"_links":{"self":[{"href":"https:\/\/www.jfdesignnet.com\/index.php?rest_route=\/wp\/v2\/posts\/1233"}],"collection":[{"href":"https:\/\/www.jfdesignnet.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.jfdesignnet.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.jfdesignnet.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.jfdesignnet.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1233"}],"version-history":[{"count":0,"href":"https:\/\/www.jfdesignnet.com\/index.php?rest_route=\/wp\/v2\/posts\/1233\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.jfdesignnet.com\/index.php?rest_route=\/wp\/v2\/media\/1238"}],"wp:attachment":[{"href":"https:\/\/www.jfdesignnet.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1233"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.jfdesignnet.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1233"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.jfdesignnet.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1233"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}