Re: Symlink indirection

From: Amos Waterland (
Date: Fri Dec 13 2002 - 12:15:16 EST

I think that you and Richard are dicussing a slightly different issue
than the original poster asked about. The original question was:

On Fri, 13 Dec 2002, Andrew Walrond wrote:
> Is the number of allowed levels of symlink indirection (if that is the
> right phrase; I mean symlink -> symlink -> ... -> file) dependant on the
> kernel, or libc ? Where is it defined, and can it be changed?

To which Richard replied:

> Since a symlink is just a file containing a name, the resulting path
> length is simply the maximum path length that user-space tools allow.
> This should be defined as "PATH_MAX". Posix defines this as 255
> characters but I think posix requires that this be the minimum and all
> file-name handling buffers must be at least PATH_MAX in length.
> A hard link is just another directory-entry for the same file. This,
> therefore follows the same rules. There must be enough space on the
> device to contain the number of directory entries, as well as enough
> buffer length in the tools necessary to manipulate these "nested"
> directories, which are not really "nested" at all.

But Richard is not actually completely correct. There is a limit of 5
levels of symlink indirection in vanilla 2.4 series Linux kernels.

  % touch 0
  % for i in `seq 1 10`; do ln -s `ls | sort | tail -1` $i; done
  % ls
  0 1 10 2 3 4 5 6 7 8 9
  % cat 5
  % cat 6
  cat: 6: Too many levels of symbolic links
  % strace cat 6 2>&1 | grep 'open("6",'
  open("6", O_RDONLY|O_LARGEFILE) = -1 ELOOP (Too many levels of symbolic links)

This has been discussed by Al Viro et al. many times on lkml. I believe
that it is not a user-space or POSIX issue, but rather a kernel issue.

Amos Waterland
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