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Comment by cperciva | Hacker News Reader

The /sbin/init binary is hard linked to /sbin/dashboard, /sbin/poweroff, /sbin/shutdown, and /sbin/wrapperd. While this technically is 5 files, it’s a single file hard linked 4 times to provide convenience commands.

Err, that's definitely 1 file with 5 directory entries, not 5 files.

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Wonder why they would use hard links instead of symlinks.

Edit: interesting, seems like there's a mild performance benefit.

https://unix.stackexchange.com/a/20716

There's a lot of benefits actually, as symbolic links often need to be handled as a completely different type of file with different semantics which often leads to bugs. Hard links are always better when you know you are dealing with a single static host & filesystem. Symbolic links in such a case are only better for indicating quickly to the user which files are linked to which others.

Reverse question: why use symlinks when you can get away with hard links?

Main thing I've seen with hard links is that deletions delete the source file which about 90% of the time isn't what an end user wants

Only if its the last hard link. If nothing else, its a wee bit of insurance from deletion since no single link removal should remove the file.

Anecdote, eons ago, we had a problem where the vendor needed to log in to the machine with the intent that they were going to upload some utilities, fix a problem, and then delete them.

Before I let them in, I set up a script that constantly scanned the directory tree they were in, and hard linked everything so I could look at what they were using later.

Clever solution!

that isn't generally how hardlinks work: you need to delete all instances of it to delete the file, as opposed to having one 'real' file like with symlinks.

That's a problem with directory hardlinks: a recursive deletion will wipe the directory (in the same way that truncate will destroy a file regardless of how many hardlinks it has). But we don't usually allow directory hardlinks these days.

It's more of a problem that changes to one linked file change the only copy. But this depends on your filesystem. Not all work this way.

Hard links only work in the same filesystem. If your system only has one volume with one filesystem (e.g. a PC) that's fine, but not a very portable option for servers.

Every one of those files is in /sbin though

Not sure it really matters that much in this case. But why not? Hard links are a quite clean and simple concept. One “object”, multiple names.

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