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karlding/cygwin-symlinks.md

Created March 24, 2018 04:39
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  1. karlding created this gist Mar 24, 2018.
    39 changes: 39 additions & 0 deletions cygwin-symlinks.md
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    # How to make Cygwin use native symlinks

    I stumbled upon this cool Cygwin option that allows you to use native Windows (NTFS) symlinks (like `CreateSymbolicLinkW` in the
    Win32 API, or `mklink` via `cmd` shell). Apparently there's a `CYGWIN`
    [environment variable](https://cygwin.com/cygwin-ug-net/using-cygwinenv.html) that "is used to configure many global settings for
    the Cygwin runtime system".

    One of those options is `winsymlinks:{lnk,native,nativestrict}`.

    > if set to just `winsymlinks` or `winsymlinks:lnk`, Cygwin creates symlinks as Windows shortcuts with a special header and the R/O
    > attribute set.
    >
    > If set to `winsymlinks:native` or `winsymlinks:nativestrict`, Cygwin creates symlinks as native Windows symlinks on filesystems and
    > OS versions supporting them.
    >
    > The difference between `winsymlinks:native` and `winsymlinks:nativestrict` is this: If the filesystem supports native symlinks and
    > Cygwin fails to create a native symlink for some reason, it will fall back to creating Cygwin default symlinks with
    > `winsymlinks:native`, while with `winsymlinks:nativestrict` the `symlink(2)` system call will immediately fail.
    >
    > For more information on symbolic links, see
    > [the section called “Symbolic links”](https://cygwin.com/cygwin-ug-net/using.html#pathnames-symlinks).
    So basically, setting the `winsymlinks` option to `nativestrict` forces Cygwin to use native symlinks!

    Normally, when you make symlinks in Cygwin, it creates plain files containing a magic cookie, followed by the path to which the
    link points to. You can read up on this in the [Cygwin documentation](https://cygwin.com/cygwin-ug-net/using.html#pathnames-symlinks).

    But with this option, we can create symlinks using `ln` and it will create NTFS-style symlinks automatically!

    ```bash
    CYGWIN=winsymlinks:nativestrict
    ln -sf /source/file /new/path
    ```

    Cool! No need to open `cmd` and manually symlink my files anymore.

    **Note**: You still need Administrator privileges, or must have the `SeCreateSymbolicLinkPrivilege`
    [privilege](https://security.stackexchange.com/questions/10194/why-do-you-have-to-be-an-admin-to-create-a-symlink-in-windows/10198#10198)
    for this to work.