Change permissions for a symbolic link

I have a symlink with these permissions:

lrwxrwxrwx 1 myuser myuser       38 Aug 18 00:36 npm -> ../lib/node_modules/npm/bin/npm-cli.js*

The symlink is located in a .tar.gz archive. Now when I unpack the tar.gz archive using maven the symlink is no longer valid. I’m therefore trying to reconstruct the symlink. First I create the symlink using ln but how do I set the same permissions as the original symlink?

Answers:

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Method 1

You can make a new symlink and move it to the location of the old link.

ln -s <new_location> npm2
mv -f npm2 npm

That will preserve the link ownership. Alternatively, you can use chown to set the link’s ownership manually.

chown -h myuser:myuser npm

On most systems, symlink permissions don’t matter. When using the symlink, the permissions of the components of symlink’s target will be checked. However, on some systems they do matter. MacOS requires read permission on the link for readlink, and NetBSD’s symperm mount option forces link permissions checks on read and traversal. On those systems (and their relatives, including FreeBSD and OpenBSD) there is a equivalent -h option to chmod.

chmod -h 777 npm

Method 2

When you try to use chmod to set the link’s permissions, the actually you do is to set the permissions of the link’s target.The link’s permissions are meaningless.

Method 3

When you have a link like:

link -> foo/bar

and want to change it to:

link -> new/target

There are two cases to consider:

1. foo/bar is not a directory or doesn’t exist or you don’t have search access to foo. Then

   ln -s new/target link

   will fail because link already exists, but you can overcome that by using the standard:

   ln -fs new/target link

2. foo/bar is a directory (and you have search permission to foo to be able to determine that foo/bar is a directory). In that case, when you do:

   ln -s new/target link

   or

   ln -fs new/target link

   That’s understood as creating a new target symlink inside the link directory (link is a directory because it’s a symlink to the foo/bar directory). So you’ll actually create a:

   foo/bar/target -> new/target

   To overcome that, GNU ln has a -T option for the link name to always be considered as link name, and not as a directory to create the link(s) in. So, with GNU ln:

   ln -fsT new/target link

   will work. Like before, it will remove the original link symlink and create it anew with new/target as the target (and the process’ euid and egid as the owner).

   GNU ln also has a -n option. It works like -T except when link is actually a real directory in which case it will still create the symlink inside that directory (instead of failing with an error).

   Portably, your best option is to remove the link first and then recreate it:

   rm -f link && ln -s new/target link

On most systems, permissions on symlinks are ignored and generally fixed to rwxrwxrwx.

On systems where symlink permissions matter (like OS/X where you need read permission to a symlink to be able to resolve its target), there’s generally a way to change them (chmod -h on OS/X).

Ownership, while like above not relevant for access to the file pointed to by the symlink on most systems, can have some other relevance wrt the t bit of the parent directory or quotas…) and there’s a standard command to change it:

chown -h user[:group] the-link
chgrp -h group the-link

Method 4

If you really need to change symlinks permission (usually meaningless, as written in other answers), I was successful with using -R option of chown:

chown -R myuser:mygroup link

If -R was not used, the permissions were not changed.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0