Changing inode value of a hardlink Post: 302905670

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Top Forums Shell Programming and Scripting Changing inode value of a hardlink Post 302905670 by Don Cragun on Friday 13th of June 2014 02:06:16 AM

06-13-2014

Registered User

Quote:

Originally Posted by fhill2

is it possible to change the inode value/ file path of a hard link?

Why do you care what i-node number is assigned to a file?

Of course it is possible. All you have to do is figure out the structure of the filesystem used to store the file and dig into the bits on disk and in the kernel's memory (if the file is open, or any of its data is cached) to change the filesystem's idea of what the i-node is for that file. Depending on the filesystem type, that might mean changing a few bits in one location, or it might mean changing lots of blocks. Using this method, you could change the i-node to be any unused i-node number available in that filesystem. (Note that if you don't already know how to do this, it is not something you should even consider trying; if you do it wrong, you may lose all of the data on that filesystem. And, if it is cached in the kernel and you get it wrong there, you may lose all of the data on all of your filesystems.)

More portably, you could copy the file to another name and then rename the new file to have the name of the old file. This will create a new file with a different i-node number and then remove the old link to the old i-node number. Of course, if there were multiple hard links to the old name, the other links will remain unchanged. If you want them to be linked to the new i-node number, you'll have to find all of the old links, unlink them and then link them to the new file. Using this method, the i-node number will be different, but you will not be able to specify what the new i-node number will be.

Don Cragun

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hardlink

hardlink(1)						      General Commands Manual						       hardlink(1)

NAME

       hardlink - Link multiple copies of a file

SYNOPSIS

       hardlink [option]...  [directory|file]...

DESCRIPTION

       hardlink is a tool which replaces copies of a file with hardlinks, therefore saving space.

OPTIONS

       -h or --help
	      print quick usage details to the screen.

       -v or --verbose
	      More verbose output. If specified once, every hardlinked file is displayed, if specified twice, it also shows every comparison.

       -n or --dry-run
	      Do not act, just print what would happen

       -f or --respect-name
	      Only try to link files with the same (basename).

       -p or --ignore-mode
	      Link/compare files even if their mode is different. This may be a bit unpredictable.

       -o or --ignore-owner
	      Link/compare files even if their owner (user and group) is different. It is not predictable

       -t or --ignore-time
	      Link/compare files even if their time of modification is different. This will retain the newest timestamp, unless -m or -M is given.

       -m or --maximize
	      Try to maximize the link count of the files.

       -M or --minimize
	      Try to minimize the link count of the files.

       -x or --exclude
	      A regular expression which excludes files from being compared and linked.

       -i or --include
	      A  regular  expression to include files. If the option --exclude has been given, this option re-includes files which would otherwise
	      be excluded. If the option is used without --exclude, only files matched by the pattern are included.

ARGUMENTS

       hardlink takes one or more directories which will be searched for files to be linked.

BUGS

       hardlink assumes that the trees it operates on do not change during operation. If a tree does change, the result is  undefined  and  poten-
       tially  dangerous.  For example, if a regular file is replaced by a device, hardlink may start reading from the device. If a component of a
       path is replaced by a symbolic link or file permissions change, security may be compromised. Do not run hardlink on a changing tree or on a
       tree controlled by another user.

AUTHOR

       The  program  hardlink  and  this manpage have been written by Julian Andres Klode, and are licensed under the MIT license. See the code of
       hardlink for further information.

0.2.0								    2012-02-28							       hardlink(1)