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--- linux:reiserfs [2009/05/25 00:35]
127.0.0.1 external edit
+++ linux:reiserfs [2016/03/16 22:57] (current)
82.50.77.129 [REISERFS error (device dm-6): vs-7000 search_by_entry_key: search_by_key returned item position == 0]
@@ Line 1: / Line 1: @@
 ====== ReiserFS & Linux ======
+===== Troubleshooting =====
+==== Basic rules of fixing b0rken ReiserFS partion ====
+//The most important things I've learned while drinking with Hans Reiser and things that always saved my data on reiserfs.//
+  * make sure you have "enough" RAM
+  * **make sure you have working (not br0ken) RAM**
+  * before running any --rebuild-sb or --rebuild-tree make sure you have backup!
+  * have the latest reiserfsprogs tools
+  * have a decent stable linux kernel and reiserfs support in it
+==== REISERFS error (device dm-6): vs-7000 search_by_entry_key: search_by_key returned item position == 0   ====
+<code>
+ReiserFS: hdx1: found reiserfs format "3.6" with standard journal
+ReiserFS: hdx1: using ordered data mode
+ReiserFS: hdx1: journal params: device hda1, size 8192, journal first block 18, max trans len 1024, max batch 900, max commit age 30, max trans age 30
+ReiserFS: hdx1: checking transaction log (hda1)
+ReiserFS: hdx1: warning: vs-7000: search_by_entry_key: search_by_key returned item position == 0
+ReiserFS: hdx1: found reiserfs format "3.6" with standard journal
+ReiserFS: hdx1: using ordered data mode
+ReiserFS: hdx1: journal params: device hda1, size 8192, journal first block 18, max trans len 1024, max batch 900, max commit age 30, max trans age 30
+ReiserFS: hdx1: checking transaction log (hda1)
+ReiserFS: hdx1: warning: vs-7000: search_by_entry_key: search_by_key returned item position == 0
+</code>
+   reiserfsck --rebuild-sb /dev/hdx1
+<code>
+Reiserfs super block in block 16 on 0x301 of format 3.6 with standard journal
+Count of blocks on the device: 4883744
+Number of bitmaps: 150
+Blocksize: 4096
+Free blocks (count of blocks - used [journal, bitmaps, data, reserved] blocks): 3430669
+Root block: 4096104
+Filesystem is clean
+Tree height: 5
+Hash function used to sort names: not set
+Objectid map size 972, max 972
+Journal parameters:
+        Device [0x0]
+        Magic [0x0]
+        Size 8193 blocks (including 1 for journal header) (first block 18)
+        Max transaction length 1024 blocks
+        Max batch size 900 blocks
+        Max commit age 30
+Blocks reserved by journal: 0
+Fs state field: 0x0:
+sb_version: 2
+inode generation number: 2442403
+UUID: bfd1afad-a173-40a6-bbbe-643dc9e68a23
+LABEL:
+Set flags in SB:
+</code>
+**Super block seems to be correct**, but here comes the trick ..
+<code>
+mount -t reiserfs /dev/hda1 /media/restore
+mount: wrong fs type, bad option, bad superblock on /dev/hda1,
+       missing codepage or other error
+       In some cases useful info is found in syslog - try
+       dmesg | tail  or so
+</code>
+Ok .. here is a workaround to make the partition mountable again it is enough to change
+one byte in the super block from 0 (hash is not set) to 3 (r5 hash).
+It can be done by a hex editor.
+<code>
+hexdump -C of block #16 (reiserfs uses 4k-size blocks, numbers start with 0):
+...
+00000030  06 00 01 00 52 65 49 73  45 72 32 46 73 00 00 00  |....ReIsEr2Fs...|
+00000040  03 00 00 00 05 00 c6 04  02 00 00 00 89 28 00 00  |......ф.....┴(..|
+          ^^
+          this byte.
+...
+</code>
+Which can be done like ..
+I used dd to copy first 512Kb from disk, then modify them and copy back to disk:
+   $ dd if=/dev/hdx1 count=1000 of=/tmp/hdx1dump
+then use your favourite Hexeditor to fix problem
+(position 0001:0040 in this file) --> write \"03\" in position 0001:0040
+and copy it back to disk
+   $ dd of=/dev/hdx1 count=1000 if=/tmp/hdx1dump