translucency8
Overlays file-systems
Usage
insmod translucency
Overview
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
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
Notes
This version requires /tmp to be writeable.
Known bugs
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!
Version
This manual page applies to translucency 0.6.0