NAME
unionimap − a tool to manipulate Unionfs inode map files.
SYNOPSIS
unionimap [ -c ] FORWARDMAP
unionimap [ -a FORWARDMAP ] REVERSEMAP PATH
unionimap [ -d ] MAP
DESCRIPTION
unionimap By default, Unionfs generates a different set of inode numbers each time you mount a file system. Additionally, the inode numbers used for reading directories is different than those reported by stat. This can confuse some utilities, and prevents NFS exports from gracefully handing remounts or server restarts.
To alleviate these problems, Unionfs supports persistent inode maps. unionimap is a utility that will generate the inode map files to be loaded at mount time by Unionfs. An inode map consists of two main components, a forward map which translates Unionfs inode numbers to lower-level inode numbers and a lower-level file system, and several reverse maps that are each associated with a single lower-level file system. Note that the maps are associated with file systems, and not branches. This means that if you have two branches on the same lower-level file system, they use only a single reverse map.
OPTIONS
|
-c |
create a forward map file. This option takes the filename of the forward map to create as an argument. This file name can be the absolute path to the file that you want to create or you can create it in the local directory and then move it. | ||
|
-a |
creates a reverse map file and adds it to a forward map file. The -a flag itself takes the forward map to add the new reverse map into. The remaining two arguments are the filename of the reverse map and then a path to the file system you wish to create the map for. This will allow the map to have the appropriate fsid for the file system that you are adding to the map. If the file system in question does not return a fsid (i.e., it returns 0 for that value in stat), then one will be created based on the device’s major and minor numbers. | ||
|
-d |
dump the contents of either a forward or reverse map. Specify multiple times for more output. If -d is specified once, then the header information for the map is printed. If -d is specified twice, then the contents of the map are also printed. For a forward map the contents are keys of a Unionfs inode number and the value is a pair of file system numbers and lower inode numbers. For the reverse map, the key is a lower-level inode number, and the value is a Unionfs inode number. |
USAGE EXAMPLE
unionimap -c /tmp/foo.forward
Create a map named foo.forward in /tmp/
unionimap -a /tmp/foo.forward /tmp/foo.reverse /tmp/
Create a map named foo.reverse in /tmp using /tmp as the directory to build the fsid from and add it to the forward map located in /tmp/foo.forward
unionimap -a /tmp/foo.forward /tmp/foo.reverse2 /n/other
Create a map named foo.reverse2 in /tmp using /n/other as the directory to build the fsid from and add it to the forward map located in /tmp/foo.forward
unionimap -d /tmp/foo.forward
Display the header contents of /tmp/foo.forward
unionimap -d -d /tmp/foo.forward
Display the header and body contents of /tmp/foo.forward
AUTHORS
Charles Wright <cwright [AT] cs.edu>, David Quigley <dquigley [AT] ic.edu>, Erez Zadok <ezk [AT] cs.edu>