When I save a file with Vim, the file permissions are changed.

How do I configure Vim to save a file without changing the file permissions? This may happen, if the ‘backupcopy’ option is set to ‘no’ or ‘auto’. Note that the default value for this option is set in such a way that this will correctly work in most of the cases. If the default doesn’t work for you, try setting the ‘backupcopy’ option to ‘yes’ to keep the file permission when saving a file:

    :set backupcopy=yes

This applies, only if you have configured Vim to make a backup whenever overwriting a file. By default, Vim will not backup files.