translucency - overlays file-systems

insmod translucency echo "/layer/1 -> /layer/2" > /proc/sys/translucency/0 # alternatively, use mount.translucency echo 65534 > /proc/sys/translucency/uid echo 16 > /proc/sys/translucency/flags

translucency will install modified syscall handlers that redirect file operations in such a way as to logically merge several directories (presumably on different file-systems, on different media) into one directory.

Options can no longer be given at module loading time. Instead they have to be written into the appropriate /proc/sys/translucency/<option> file.

[0-9]*

are overlay entries used as seen above: /layer/1 is lower layer - write access is redirected away. /layer/2 is upper layer - written files go here

uid=<int>

limits overlaying to user with EUID <int>

gid=<int>

limits overlaying to group with EGID <int>

fs=<int>

limits overlaying of mounts to filesystems with this magic number <int> ; negative values mean all except the given one ; for values see grep SUPER_MAGIC /usr/include/linux/*.h

flags=<int>

change the module's operation with a bitwise combination of the following:

1=no_translucency:

turns module off

2=no_copyonwrite:

kernel does not try to copy files if needed (i.e. for appending)

4=no_getdents:

turn off merging directories - only entries in lower layer are shown in directory listings

8=do_downcase:

downcase all filenames to avoid inconsistencies on case-insensitive filesystems

16=no_whiteout:

do not automatically create whiteout entries which allow for renaming and deletion of files on r/o filesystems

This version requires /tmp to be writeable.

Bad symlink handling Bad .. handling after chdir into a dir that only exists in overlay rmdir and rm -r are often not able to remove a directory stating that is not empty (it contains white-out entries) There are probably serious buffer overflow conditions left in this module. Suggestions for improving the security of this module are welcome!

Report bugs through the bug-tracking system at http://sourceforge.net/projects/translucency/

Bernhard M. Wiedemann <b.m.w@gmx.net> David Bird <dbird@bpnetworks.com>

The effect is somewhat similar to: inheriting (ifs), stacking (fist), translucent (tfs), loopback (lofs), overlaying (ovlfs), and BSDs union file system

This manual page applies to translucency 0.6.0