symbolic linls

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symbolic linls

Franz Fehringer
Dear Cygwin community,

As i understand Cygwin will soon no longer support Windows XP resp.
2003. This means that only Windows versions with native symbolic link
functionality will be supported after that. Would it be possible to use
only native symbolic links throughout esp. during setup.exe?

Best regards

Franz


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Re: symbolic linls

David Macek
On 5. 8. 2016 13:24, Franz Fehringer wrote:
> Dear Cygwin community,
>
> As i understand Cygwin will soon no longer support Windows XP resp.
> 2003. This means that only Windows versions with native symbolic link
> functionality will be supported after that. Would it be possible to use
> only native symbolic links throughout esp. during setup.exe?

Short answer: No.

Long answer:

There are limitations to NTFS symlinks, other than OS support, that make them incompatible with POSIX symlinks. See <https://cygwin.com/cygwin-ug-net/using.html#pathnames-symlinks> and <https://github.com/git-for-windows/git/wiki/Symbolic-Links> for more information.

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David Macek


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Re: symbolic linls

Andrey Repin
Greetings, David Macek!

>> As i understand Cygwin will soon no longer support Windows XP resp.
>> 2003. This means that only Windows versions with native symbolic link
>> functionality will be supported after that. Would it be possible to use
>> only native symbolic links throughout esp. during setup.exe?

> Short answer: No.

> Long answer:

> There are limitations to NTFS symlinks, other than OS support, that make
> them incompatible with POSIX symlinks. See
> <https://cygwin.com/cygwin-ug-net/using.html#pathnames-symlinks> and
> <https://github.com/git-for-windows/git/wiki/Symbolic-Links> for more information.

There's limitations, yes. But what do you mean by "incompatibility" ?


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With best regards,
Andrey Repin
Wednesday, August 10, 2016 04:16:00

Sorry for my terrible english...


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Re: symbolic linls

Warren Young-2
On Aug 9, 2016, at 7:16 PM, Andrey Repin wrote:

>
>>> As i understand Cygwin will soon no longer support Windows XP resp.
>>> 2003. This means that only Windows versions with native symbolic link
>>> functionality will be supported after that. Would it be possible to use
>>> only native symbolic links throughout esp. during setup.exe?
>
>> Short answer: No.
>
>> Long answer:
>
>> There are limitations to NTFS symlinks, other than OS support, that make
>> them incompatible with POSIX symlinks. See
>> <https://cygwin.com/cygwin-ug-net/using.html#pathnames-symlinks> and
>> <https://github.com/git-for-windows/git/wiki/Symbolic-Links> for more information.
>
> There's limitations, yes. But what do you mean by "incompatibility” ?

I’d say “breaking every shell script that calls ln(1) just because it isn’t running as Administrator” would be an incompatible change, for one.


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Re: symbolic linls

David Macek
In reply to this post by Andrey Repin
On 10. 8. 2016 3:16, Andrey Repin wrote:

> Greetings, David Macek!
>
>>> As i understand Cygwin will soon no longer support Windows XP resp.
>>> 2003. This means that only Windows versions with native symbolic link
>>> functionality will be supported after that. Would it be possible to use
>>> only native symbolic links throughout esp. during setup.exe?
>
>> Short answer: No.
>
>> Long answer:
>
>> There are limitations to NTFS symlinks, other than OS support, that make
>> them incompatible with POSIX symlinks. See
>> <https://cygwin.com/cygwin-ug-net/using.html#pathnames-symlinks> and
>> <https://github.com/git-for-windows/git/wiki/Symbolic-Links> for more information.
>
> There's limitations, yes. But what do you mean by "incompatibility" ?
I mean differences between how NTFS symlinks work and how POSIX symlinks (that Cygwin apps expect) work. It's described on the Git-for-Windows page I linked. Quoting:

> You need the SeCreateSymbolicLinkPrivilege privilege, which is by default assigned only to Administrators but can be assigned to normal users using Local Security Policy (or via Active Directory). Note that regardless of privilege assignment, members of the Administrators group will also require UAC elevation.

> Symbolic links on remote filesystems are disabled by default (call fsutil behavior query SymlinkEvaluation to find out)

> Symbolic links will only work on NTFS, not on FAT

> Windows' symbolic links are typed: they need to know whether they point to a directory or to a file

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David Macek


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Re: symbolic linls

Andrey Repin
Greetings, David Macek!

>>>> As i understand Cygwin will soon no longer support Windows XP resp.
>>>> 2003. This means that only Windows versions with native symbolic link
>>>> functionality will be supported after that. Would it be possible to use
>>>> only native symbolic links throughout esp. during setup.exe?
>>
>>> Short answer: No.
>>
>>> Long answer:
>>
>>> There are limitations to NTFS symlinks, other than OS support, that make
>>> them incompatible with POSIX symlinks. See
>>> <https://cygwin.com/cygwin-ug-net/using.html#pathnames-symlinks> and
>>> <https://github.com/git-for-windows/git/wiki/Symbolic-Links> for more information.
>>
>> There's limitations, yes. But what do you mean by "incompatibility" ?

> I mean differences between how NTFS symlinks work and how POSIX symlinks
> (that Cygwin apps expect) work. It's described on the Git-for-Windows page I linked. Quoting:

>> You need the SeCreateSymbolicLinkPrivilege privilege, which is by default
>> assigned only to Administrators but can be assigned to normal users using
>> Local Security Policy (or via Active Directory). Note that regardless of
>> privilege assignment, members of the Administrators group will also require
>> UAC elevation.

That's limitation, but not necessarily an incompatibility.
Do note "members of Administrators group". If your account is not a member of
administrators group (which I don't see as necessity in everyday use), this
will work transparently.
Having ~14 years of experience, going through "all admin" in Win'9x to
"default admin" in NT/2k, and "admin with UAC" in Vista+, I'm strongly
considering excluding my account from Admins/Domain Admins group for my
upcoming home AD that I'm preparing to solve some of the interoperability
limitations of POSIX permissions system. Or, more precisely, limitations of
Samba's treatment of POSIX permissions system :/ One can only wonder, why they
have gone such a route.

>> Symbolic links on remote filesystems are disabled by default (call fsutil
>> behavior query SymlinkEvaluation to find out)

Symlinks on remote FS didn't work straight in the best times.

>> Symbolic links will only work on NTFS, not on FAT

That's a given.

>> Windows' symbolic links are typed: they need to know whether they point to
>> a directory or to a file

This is of no concern for an application.


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With best regards,
Andrey Repin
Wednesday, August 10, 2016 13:31:16

Sorry for my terrible english...


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Re: symbolic linls

David Macek
On 10. 8. 2016 12:46, Andrey Repin wrote:
>>> Windows' symbolic links are typed: they need to know whether they point to
>>> a directory or to a file
>
> This is of no concern for an application.

This is actually the worst problem with NTFS symlinks. The symlink becomes unreadable/untraversable if its type doesn't match the target's type. The most prominent example where this is an issue is creating symlinks to non-existent targets.

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David Macek


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