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Diffstat (limited to 'winsup/doc/filemodes.sgml')
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diff --git a/winsup/doc/filemodes.sgml b/winsup/doc/filemodes.sgml new file mode 100644 index 000000000..b0bac2eef --- /dev/null +++ b/winsup/doc/filemodes.sgml @@ -0,0 +1,34 @@ +<sect1 id="using-filemodes"><title>File permissions</title> + +<para>On Windows 9x systems, files are always readable, and Cygwin uses the +native read-only mode 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>Under NT, file permissions default to the same behavior as Windows +9x but there is optional functionality in Cygwin that can make file +systems behave more like on UNIX systems. This is turned on by adding +the "ntea" option to the <EnVar>CYGWIN</EnVar> environment variable.</para> + +<para>When the "ntea" feature is activated, Cygwin will start with basic +permissions as determined above, but can store POSIX file permissions in NT +Extended Attributes. This feature works quite well on NTFS partitions +because the attributes can be stored sensibly inside the normal NTFS +filesystem structure. However, on a FAT partition, NT stores extended +attributes in a flat file at the root of the partition called <filename>EA +DATA. SF</filename>. This file can grow to extremely large sizes if you +have a large number of files on the partition in question, slowing the +system to a crawl. In addition, the <filename>EA DATA. SF</filename> file +can only be deleted outside of Windows because of its "in use" status. For +these reasons, the use of NT Extended Attributes is off by default in +Cygwin. Finally, note that specifying "ntea" in <EnVar>CYGWIN</EnVar> has no +effect under Windows 9x. </para> + +<para>Under NT, the test "[ -w filename]" is only true if filename is +writable across the board, e.g. <command>chmod +w filename</command>. </para> + +</sect1> + |