Native symbolic link behavior is broken and makes backups using Cygwin command line tools impossible

[Brian Inglis]

On 2021-01-02 21:16, Matt D. via Cygwin wrote:
> I have a folder with a lot of native Windows symbolic links. I want to
> copy this folder.
> 
> I cannot rsync or cp this folder due to Cygwin being unable to create
> symbolic links without also wanting to verify the link target. This
> can be demonstrated:
> 
> $ ln -s a b
> ln: failed to create symbolic link 'b': No such file or directory
> 
> If I create a test directory folder_a/ and folder_b/. Inside I will
> "touch a" and "ln -s a b".
> 
> I cannot rsync this folder:
> 
> $ rsync -a folder_a/ folder_b/
> rsync: symlink "folder_a/b" -> "a" failed: No such file or directory (2)
> rsync error: some files/attrs were not transferred (see previous
> errors) (code 23) at main.c(1306) [sender=3.2.0dev]
> 
> Using "cp -a folder_a/* folder_b/" in this test case DOES work but
> this is simply because files were returned in the correct order and
> the link could be created.
> 
> This can be demonstrated where this works fine:
> 
> $ cp -a folder_a/a folder_a/b folder_b/
> 
> But this does not:
> 
> $ cp -a folder_a/b folder_a/b folder_b/
> cp: cannot create symbolic link 'folder_b/b': No such file or directory
> cp: warning: source file 'folder_a/b' specified more than once
> 
> The order in which files are returned while listing them in a
> directory and necessitating their pre-existence while performing a
> deep copy is impossible. It's also very normal for symbolic links to
> exist which may or may not point to a valid target depending on the
> observing path.
> 
> Windows does NOT require a link to be valid before creation. This can
> be demonstrated with mklink:
> 
> C:\mklink b a
> symbolic link created for b <<===>> a

Depending on exactly what you have and what you want to do try:

	$ cp -av
	$ cp -dv
	$ cp -Pv
or
	> robocopy /sl

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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