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-Ext2fs Undeletion of Directory Structures mini-HOWTO
-!!!Ext2fs Undeletion of Directory Structures mini-HOWTO
-!Tomas Ericsson
-
- tomase@matematik.su.se
-
-
-
-__Revision History__Revision v0.1.114 November 2000Revised by: T.E.Initial release.
-
-
-
-
-
- This document is supposed to be as an complementary to the
-''Ext2fs-Undeletion mini-HOWTO'' written by
-Aaron Crane. I really recommend you to carefully study that one before
-reading this.
-
-
-
-
- Here I will describe a straight forward way of recovering whole
-directory structures, instead of file by file, that have been removed
-by a misplaced ''rm -rf''.
-
-
-
-
-
-
-----; __Table of Contents__; 1. Introduction: ; 1.1. Disclaimer; 1.2. License; 1.3. Feedback; 1.4. New versions of this document; 1.5. Acknowledgements; 1.6. Background; 2. Preconditions; 3. Preparation; 4. Finding inodes for deleted directories; 5. Analyse of directory dump; 6. Locating deleted inodes; 7. Activating inodes; 8. Adding directory entries; 9. Recalculation; 10. If /lost+found not empty; 11. Final touch; 12. References
-!!!1. Introduction
-!!1.1. Disclaimer
-
- The author is not responsible for damages due actions taken based on
-this document. You will do everything at your own risk.
-
-
-----
-!!1.2. License
-
- This document may be distributed only subject to the terms and
-conditions set forth in the LDP license available at
- http://www.linuxdoc.org/manifesto.html
-
-
-
-----
-!!1.3. Feedback
-
- Any kind of feedback is welcome. Corrections of errors in this text are
-of great interest. If someone find things described here useful I really
-would appreciate to hear that from you.
-
-
-----
-!!1.4. New versions of this document
-
- The latest version of this document will be found at
- http://www.matematik.su.se/~tomase/ext2fs-undeletion/
-
-
-----
-!!1.5. Acknowledgements
-
- Thanks to the following persons for correctures etc (in alphabetic
-order).
-
-
-
-
-
-
-
-*
-
-Gabriel Kihlman
-
-
-*
-*
-
-Richard Nyberg
-
-
-*
-*
-
-Mats Oldin
-
-
-*
-*
-
-Tobias Westerblom
-
-
-*----
-!!1.6. Background
-
- This text has been written while solving my own undeletion problems that
-I had some time ago. I was about to move some directories from one disk
-to another. The problem was that the extra disk went corrupted directly
-after the move for some reason.
-
-
-
-
- So I wanted to get the moved directories back from my original disk.
-There were totally about 40000 files to recover and I did not feel very
-much like to search and rename each one of them by hand.
-
-
-
-
- I wanted to get back the whole structure of directories. The same
-situation would have appeared if I had made an
-''rm -rf'' to those directories.
-
-
-----
-!!!2. Preconditions
-
- It is really important that you unmount the affected partition immediately
-before doing anything else with it. If you have copied around some files
-in this partition after the accident, then the chance for this method to
-work has lowered a lot.
-
-
-
-
- Also you must have a quite new kernel, because the
-2..x and below zeroes indirect blocks, which will
-not make this process to work for files with more than 12 blocks of data.
-
-
-
-
- I will describe one method of recovery and I will not leave out much for
-error handling. If you suspect that some step described below went wrong,
-I do not recommend you to go any further.
-
-
-----
-!!!3. Preparation
-
- Unmount the partition where you got your deleted files at. I will denote
-that partition with /dev/hdx1.
-
-
-
-
-
- # umount /dev/hdx1
-
-
-
-
- Check the size in blocks of /dev/hdx1.
-
-
-
-
-
- # fdisk -l /dev/hdx
-
-
-
-
- Now you need to have an extra partition of the same size as
-/dev/hdx1, to be able to act safely. Suppose that you
-have an empty harddrive located at /dev/hdy.
-
-
-
-
-
- # fdisk /dev/hdy
-
-
-
-
- Create a partition with the same size as /dev/hdx1.
-Here ''size'' is the size in blocks (each block is
-1024 kB) of /dev/hdx1 taken from above.
-
-
-
-
-__Note: __ I am using ''fdisk'' version 2.10f
-and if you have another version the ''fdisk''
-interaction below may not be the same.
-
-
-
-
-
- fdisk: n `- Add a new partition.
-fdisk: p `- Primary partition.
-fdisk: `- Just press return to chose the default first cylinder.
-fdisk: +sizeK `- Make a partition of the same size as /dev/hdx1.
-fdisk: w `- Write table to disk and exit.
-
-
-
-
- Now copy the content of the original partition to that extra one.
-
-
-
-
-
- # dd if=/dev/hdx1 of=/dev/hdy1 bs=1k
-
-
-
-
- This process may take quite a long time dependent of how big the partition
-is. You can get the job done faster by increasing the blocksize,
-''bs'', but then you need to get the division of the
-partition by ''bs'' to have a remainder of zero.
-
-
-
-
- From now on we will only work with that copy of the source partition to
-be able to step back if something goes wrong.
-
-
-----
-!!!4. Finding inodes for deleted directories
-
- We will try to find out the inode numbers of the deleted directories.
-
-
-
-
-
- # debugfs /dev/hdy1
-
-
-
-
- Walk to that place in the structure where the directories were located
-before the deletion. You can use ''ls'' and
-''cd'' inside ''debugfs''.
-
-
-
-
-
- debugfs: ls -l
-
-
-
-
- Example of output from the above command.
-
-
-
-
-
- 179289 20600 0 0 0 17-Feb-100 18:26 file-1
-918209 40700 500 500 4096 16-Jan-100 15:18 file-2
-160321 41777 0 0 4096 3-Jun-100 06:13 file-3
-177275 60660 0 6 0 5-May-98 22:32 file-4
-229380 100600 500 500 89891 19-Dec-99 15:40 file-5
-213379 120777 0 0 17 16-Jan-100 14:24 file-6
-
-
-
-
- Description of the fields.
-
-
-
-
-
-
-
-#
-
- Inode number.
-
-
-
-#
-#
-
- First two (or one) numbers represents the kind of inode we got:
-
-
-
-
-2 = Character device
-
-
-
-4 = Directory
-
-
-
-6 = Block device
-
-
-
-10 = Regular file
-
-
-
-12 = Symbolic link
-
-
-
- Last four numbers are the usual Unix rights.
-
-
-
-#
-#
-
- Owner in number representation.
-
-
-
-#
-#
-
- Group in number representation.
-
-
-
-#
-#
-
- Size in bytes.
-
-
-
-#
-#
-
- Date (Here we can see the Y2K bug =)).
-
-
-
-#
-#
-
- Time.
-
-
-
-#
-#
-
- Filename.
-
-
-
-#
-
- Now dump the mother directory to disk. Here ''inode'' is
-the corresponding inode number (do not forget the '`' and 'b').
-
-
-
-
-
- debugfs: dump `inodeb debugfs-dump
-
-
-
-
- Get out of ''debugfs''.
-
-
-
-
-
- debugfs: quit
-
-
-----
-!!!5. Analyse of directory dump
-
- View the dumped inode in a readable format.
-
-
-
-
-
- # xxd debugfs-dump | less
-
-
-
-
- Every entry consist of five fields. For the first two fields the bytes
-representing the field comes in backward order. That means the first byte
-is the least significant.
-
-
-
-
- Description of the fields.
-
-
-
-
-
-
-
-#
-
- Four bytes - Inode number.
-
-
-
-#
-#
-
- Two bytes - Directory entry length.
-
-
-
-#
-#
-
- One byte - Filename length (1-255).
-
-
-
-#
-#
-
- One byte - File type (-7).
-
-
-
-
-0 = Unknown
-
-
-
-1 = Regular file
-
-
-
-2 = Directory
-
-
-
-3 = Character device
-
-
-
-4 = Block device
-
-
-
-5 = FIFO
-
-
-
-6 = SOCK
-
-
-
-7 = Symbolic link
-
-
-#
-#
-
- Filename (1-255 characters).
-
-
-
-#
-
- If an entry in the directory is to be deleted, then the second field at
-the entry before will be increased by the value of the deleted entrys
-second field.
-
-
-
-
- If a filename is renamed to a shorter one, then the third field will be
-decreased.
-
-
-
-
- The first entry you will see is the directory itself, represented by a
-dot.
-
-
-
-
- Suppose that we have the following directory entry.
-
-
-
-
-
- c1 02 0e 00 40 00 05 01 'u' 't' 'i' 'l' 's'
-
-
-
-
- Then the inode would be e02c1 in hexadecimal representation or 918209 in
-decimal. The next entry would be located after 64 bytes (40 in hex). We
-see that the filename consist of 5 bytes ("utils") and the file type (01)
-is a regular file.
-
-
-
-
- Now recalculate the directories inode numbers in decimal representation.
-
-
-
-
- If you do not like to calculate this by hand I have made a small program
-in C that will do this for you. The program takes as input a directory
-dump (created by ''debugfs'' as described in
-Section 4). The output (at stdout) consist of each entrys
-inode number and filename.
-
-
-
-
- Before you run the program you need to load the dump into a hexeditor and
-change the ''directory entry length'' field at the entry
-before the one you want to get back. But it is simple. If we name the
-field before to ''x'' and the field at the entry you want
-to get back to ''y''. Then change ''x''
-to ''x - y''.
-
-
-
-
- The program called ''e2dirana'' (ext2fs directory
-analyse) can be found at
- http://www.matematik.su.se/~tomase/ext2fs-undeletion/
-
-
-----
-!!!6. Locating deleted inodes
-
- Get a list of all deleted inodes.
-
-
-
-
-
- # echo lsdel | debugfs /dev/hdy1 b lsdel.out
-
-
-
-
- One problem here is that ''debugfs'' will not give the
-inode numbers to files that are zero in size (you probably have some in
-your /etc directory for instance). I will tell how to solve this problem
-in Section 9 and Section 11.
-
-
-
-
- Load "lsdel.out" into a texteditor. The list of inodes should be sorted in
-time. Try to remember exactly what time you did that
-''rm -rf''. Probably it was the the last items you
-deleted and then they will be located at the bottom of the list, because it
-is sorted in time. Delete all lines that has nothing of interest. Save as
-"lsdel.out-selected".
-
-
-
-
- Now we will cut away everything except the inodes.
-
-
-
-
-
- # cut -b 1-8 lsdel.out-selected | tr -d " " b inodes
-
-
-
-
- To be sure, check that the deleted directories found above have their
-inodes in the list.
-
-
-
-
-
- # grep ^inode$ inodes
-
-
-
-
- Where ''inode'' is the corresponding inode number.
-
-
-----
-!!!7. Activating inodes
-
- Now it is time for changing some flags of the deleted inodes.
-
-
-
-
- Copy the following 6 lines into a file named "make-debugfs-input".
-
-
-
-
-
- #!/bin/sh
-awk '{ print "mi `" $1 "b\n"\
-"\n\n\n\n\n\n\n"\
-"\n"\
-"1\n"\
-"\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n" }'
-
-
-
-
- This will simulate the user input when editing the inodes manually.
-We will set ''deletion time'' to
-and ''link count'' to 1.
-
-
-
-
-__Note: __ I am using ''debugfs'' version 1.18 and if you have
-another version you should check if you need to adjust the number of
-returns above.
-
-
-
-
- Now change the inodes.
-
-
-
-
-
- # ./make-debugfs-input ` inodes | debugfs -w /dev/hdy1 | tail -c 40
-
-
-
-
- If all went well it should end with "Triple Indirect Block
[[
] debugfs:".
-
-
-----
-!!!8. Adding directory entries
-
- Start up ''debugfs'' in read-write mode.
-
-
-
-
-
- # debugfs -w /dev/hdy1
-
-
-
-
- Now you should add the deleted directories to the directory were they were
-located before deletion.
-
-
-
-
-
- debugfs: link `inodeb directoryname
-
-
-
-
- Where ''inode'' is the inode number and
-''directoryname'' is the directoryname.
-
-
-
-
- After you have added the links you will notice that the directories have
-popped up in the current directory. You can now list their contents (from
-''debugfs'').
-
-
-
-
- But the size shown for each directory is zero and that need to be fixed,
-otherwise they will look empty with ''ls'' from the
-shell.
-
-
-
-
- Get out of ''debugfs''.
-
-
-
-
-
- debugfs: quit
-
-
-----
-!!!9. Recalculation
-
- Now it is time to call ''e2fsck'' to recalculate the
-sizes and checksums.
-
-
-
-
-__Note: __ I am using ''e2fsck'' version 1.18 and if you have
-another version you should check if some parameters or interaction have
-changed.
-
-
-
-
- If you know that you do ''not'' have any files with the
-size of zero that you want to recover you can do the following and skip
-the rest of this section (Of course you can leave out the
-''y'' parameter, but then you need to answer all
-questions by hand and it may take a lot of time.).
-
-
-
-
-
- # e2fsck -f -y /dev/hdy1 b e2fsck.out 2b81
-
-
-
-
- If you instead want the zero files back you have to answer
-''no'' to all questions about clearing entries and
-''yes'' to the other ones.
-
-
-
-
- Copy the following 7 lines into a file named "e2fsck-wrapper".
-
-
-
-
-
- #!/usr/bin/expect -f
-set timeout -1
-spawn /sbin/e2fsck -f $argv
-expect {
-"Clear`yb? " { send "n" ; exp_continue }
-"`yb? " { send "y" ; exp_continue }
-}
-
-
-
-
- Run the script.
-
-
-
-
-
- # ./e2fsck-wrapper /dev/hdy1 b e2fsck.out 2b81
-
-
-
-
- Examine "e2fsck.out" to see what ''e2fsck'' thought about
-your partition.
-
-
-----
-!!!10. If /lost+found not empty
-
- Some of the directory and files may not pop-up at their right places.
-Instead they will be located in /lost+found with names after their inode
-numbers.
-
-
-
-
- In this case the pointer at the ".." directory entry probably have been
-increased and will point to one of the later entrys in the directory (of
-some reason I do not know, maybe it is a fs bug).
-
-
-
-
- Examine ''pass 3'' (where directory connectivity is
-checked) of "e2fsck.out". There you will find which directories that are
-affected. Dump those to disk (as described in Section 4).
-
-
-
-
- Run
- ''e2dirana''
-both with and without the ''p'' parameter (it changes the
-pointer at the ".." directory entry). Here ''dump'' is
-the dumped directory.
-
-
-
-
-
- # e2dirana dump b dump1
-# e2dirana -p dump b dump2
-
-
-
-
- Compare the outputs.
-
-
-
-
-
- # diff dump1 dump2
-
-
-
-
- If they are not the same there are missing files in that directory. Then
-move those files from /lost+found to their right place. Here
-''dest'' is a symbolic link to the destination directory.
-Put the output in a script and run it if you agree.
-
-
-
-
-
- # diff dump1 dump2 |\
-tail -n $[[`diff dump1 dump2 | wc -l`-1] | cut -b 3- |\
-sed -e 's/^\([[^ ]*\) \(.*\)$/mv lost+found\/#\1 dest\/"\2"/' |\
-sed -e 's/!/"\\\!"/g'
-
-
-
-
- Repeat all this until /lost+found is empty.
-
-
-----
-!!!11. Final touch
-
- If in Section 9 you choosed to get files with the size of
-zero back you now have a problem, because those files has a non-zero
-deletion time and their link count is zero. That means that every time
-''e2fsck'' is running it will prompt to remove (clear)
-those files.
-
-
-
-
- The easy way to solve this is to copy the whole directory structure to
-another place (it can be the same partition) and then delete the old
-directory structure. Otherwise you will have to locate those inodes and
-change them with ''debugfs''.
-
-
-
-
- Now if everything have went well, things should have been restored to its
-original state before deletion. At least it did for me and in those tests
-I have made while writing this. Be sure that you have brought up to the
-preconditions described in Section 2.
-
-
-----
-!!!12. References
-
- ''Linux Ext2fs Undeletion mini-HOWTO'', v1.3
-
-
-
-
-
-
-
-*
-
-Aaron Crane
-
-
-*
-
- ''Design and Implementation of the Second Extended Filesystem'',
- http://e2fsprogs.sourceforge.net/ext2intro.html
-
-
-
-
-
-
-
-*
-
-Rémy Card, Laboratoire MASI--Institut Blaise Pascal
-
-
-*
-*
-
-Theodore Ts'o, Massachussets Institute of Technology
-
-
-*
-*
-
-Stephen Tweedie, University of Edinburgh
-
-
-*
-
- ''Kernel Source for Linux 2.2.16''
-
-
-
-
-
-
-
-*
-
-linux/include/linux/ext2_fs.h
-
-
-*
-*
-
-linux/fs/ext2/namei
.c
-
-
-*
+Describe
[HowToExt2fsUndeletionDirStruct
] here
.
