How do file permissions work with partition filesystem?

Question

If I store a file in ext2, ext3, or ext4 formatted partition, it's permission is saved. I mean, I can have different permissions for different files in extX partition. However, If I store a file in NTFS partition, I can't change it's permission. The permission is depends on how NTFS partition is mounted. For example, with nautilus, all file permissions will be rwxrwxrwx.

It can bring some problems if I backed up some files that need different permissions from extX to NTFS. Two files with rw------- and rw-r--r-- permissions will have rwxrwxrwx permissions if stored in NTFS.

My points here is (which basically one point in the title):

1. Where is the information about file permission stored?
   • If it stored in OS configuration, how can I get exactly the same permission if I reinstall the OS.
   • If it stored in the file it self, does it means file state is changed when copying from extX to NTFS and vice versa?
2. If I have a lot of files with different permissions, then copy all of them to NTFS. Is it possible to get back the exact permissions for all file if I copy all of them back to extX?
3. Is it possible to have different file permissions in NTFS?

Answer 1

The permissions are stored in file system metadata. NTFS and ext3/4 file systems differ substantially in how they store metadata. One solution would be to create a tar file of the source directory (with or without compression), writing the resulting file to the NTFS file system. When the content of the tar archive is extracted to a ext3/4 file system the permissions and ownership are preserved.

For example:

tar cvf /mnt/ntfs_share/archive.tar /source_ext4/*

Or, with bzip2 compression:

tar cjvf /mnt/ntfs_share/archive.tar.bz2 /source_ext4/*