newlib-cygwin/winsup/doc/filemodes.xml

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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
		"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">

<sect1 id="using-filemodes"><title>File permissions</title>

<para>On FAT or FAT32 filesystems, files are always readable, and Cygwin
uses the DOS read-only attribute to determine if they are writable. Files are
considered to be executable if the filename ends with .bat, .com or .exe, or
if its content starts with #!. Consequently <command>chmod</command> can
only affect the "w" mode, it silently ignores actions involving the other
modes.  This means that <command>ls -l</command>
needs to open and read files. It can thus be relatively slow.</para>

<para>On NTFS, file permissions are evaluated using the Access Control
Lists (ACLs) attached to a file.  This can be switched off by using the
"noacl" option to the respective mount point in the
<filename>/etc/fstab</filename> or <filename>/etc/fstab.d/$USER</filename>
file.  For more information on file permissions, see

<!-- TODO: Put the file permission stuff from ntsec here??? -->

<xref linkend="ntsec"></xref>.
</para>

<!-- TODO -->

<para>On NFS shares, file permissions are exactly the POSIX permissions
transmitted from the server using the NFSv3 protocol, if the NFS client
is the one from Microsoft's "Services For Unix", or the one built into
Windows Vista or later.
</para>

<para>Only the user and group ownership is not necessarily correct.</para>

</sect1>