{"id":754,"date":"2015-05-08T16:51:50","date_gmt":"2015-05-09T01:51:50","guid":{"rendered":"http:\/\/blog.box.kr\/?p=754"},"modified":"2015-05-08T16:51:50","modified_gmt":"2015-05-09T01:51:50","slug":"repair-a-broken-ext4-superblock-in-ubuntu","status":"publish","type":"post","link":"https:\/\/blog.box.kr\/?p=754","title":{"rendered":"Repair a broken Ext4 Superblock in Ubuntu"},"content":{"rendered":"

This has happened to me a few times, and it\u2019s not a nice problem to find yourself in. You computer won\u2019t boot, all your filesystem checks tell you you\u2019ve a bad superblock, but you cant seem to find how to fix it. Well, here goes\u00a0<\/span>\ud83d\ude42<\/span><\/p>\n

This guide is for ext4 , though I\u2019ll explain how other filesystems can be cured along the way. The easiest way to carry all this out, seeing as your computer probably won\u2019t boot at this stage, is to download and burn a copy of\u00a0<\/span>Parted Magic<\/a>. Boot from that, and you\u2019ll access to a number of useful tools.<\/p>\n

First, figure out what partition we\u2019re dealing with.<\/p>\n

\n
\n
\n\n\n\n
\n
1\n<\/div>\n<\/td>\n
\n
\n
sudo<\/code> fdisk<\/code> -l<\/code>\n<\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/blockquote>\n

The above will list all the partitions on all the drives in your computer. To recover a lost partition, your going to need\u00a0<\/span>Testdisk<\/a>. Testdisk is included in Parted Magic, and there\u2019s a great guide on their site. For this though, we just need the partition number, such as \/dev\/sda3 or \/dev\/hdb1.<\/p>\n

Now, make sure your superblock is the problem, by starting a filesystem check, replacing xxx with your partition name. Here, you can change ext4 to ext3, or ext2 to suit the filesystem.<\/p>\n

\n
\n
\n\n\n\n
\n
1\n<\/div>\n<\/td>\n
\n
\n
sudo<\/code> fsck<\/code>.ext4 -<\/code>v<\/code> \/dev\/xxx<\/code>\n<\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/blockquote>\n

If your superblock is corrupt, the output will look like this<\/p>\n

\n
\n
\n\n\n\n
\n
1\n<\/div>\n
2\n<\/div>\n
3\n<\/div>\n
4\n<\/div>\n
5\n<\/div>\n
6\n<\/div>\n
7\n<\/div>\n
8\n<\/div>\n
9\n<\/div>\n
10\n<\/div>\n
11\n<\/div>\n<\/td>\n
\n
\n
fsck<\/code> \/dev\/sda5<\/code>\n<\/div>\n
fsck<\/code> 1.41.4 (27-Jan-2009)<\/code>\n<\/div>\n
e2fsck 1.41.4 (27-Jan-2009)<\/code>\n<\/div>\n
fsck<\/code>.ext4: Group descriptors <\/code>look<\/code> bad... trying backup blocks...<\/code>\n<\/div>\n
fsck<\/code>.ext4: Bad magic number <\/code>in<\/code> super-block <\/code>while<\/code> trying to <\/code>open<\/code> \/dev\/sda5<\/code>\n<\/div>\n
\n<\/div>\n
The superblock could not be <\/code>read<\/code> or does not describe a correct ext4<\/code>\n<\/div>\n
filesystem.\u00a0 If the device is valid and it really contains an ext4<\/code>\n<\/div>\n
filesystem (and not swap or ufs or something <\/code>else<\/code>), <\/code>then<\/code> the superblock<\/code>\n<\/div>\n
is corrupt, and you might try running e2fsck with an alternate superblock:<\/code>\n<\/div>\n
e2fsck -b 8193 &lt;device&gt;<\/code>\n<\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/blockquote>\n

Now lets find where your superblock backups are kept.<\/p>\n

\n
\n
\n\n\n\n
\n
1\n<\/div>\n<\/td>\n
\n
\n
sudo<\/code> mke2fs -n <\/code>\/dev\/xxx<\/code>\n<\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/blockquote>\n

Down at the bottom of this output, should be a list of the backups<\/p>\n

\n

\n

\n
\n\n\n\n
\n
1\n<\/div>\n
2\n<\/div>\n<\/td>\n
\n
\n
Superblock backups stored on blocks:<\/code>\n<\/div>\n
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208<\/code>\n<\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/blockquote>\n

Your almost there. Finally, restore the superblock from the backup, again replacing the x\u2019s with your partition name, and block_number with the first backup superblock.<\/p>\n

\n

\n

\n
\n\n\n\n
\n
1\n<\/div>\n<\/td>\n
\n
\n
sudo<\/code> e2fsck -b block_number <\/code>\/dev\/xxx<\/code>\n<\/div>\n<\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/blockquote>\n

Now reboot, and your superblock should be fixed. If it\u2019s not, repeat the steps, but restore a different backup superblock\u00a0<\/span>\ud83d\ude42<\/span><\/p>\n

\n

\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":"

This has happened to me a few times, and it\u2019s not a nice problem to find yourself in. You computer won\u2019t boot, all your filesystem checks tell you you\u2019ve a bad superblock, but you cant seem to find how to fix it. Well, here goes\u00a0\ud83d\ude42 This guide is for ext4 , though I\u2019ll explain how other filesystems can be cured along the way. The easiest way to carry all this out, seeing as your computer probably won\u2019t boot at this stage, is to download and burn a copy of\u00a0Parted Magic. Boot from that, and you\u2019ll access to a number of useful tools. First, figure out what partition we\u2019re dealing with. 1 sudo fdisk -l The above will list all the partitions on all the drives in your computer. To recover a lost partition, your going to need\u00a0Testdisk. Testdisk is included in Parted Magic, and there\u2019s a great guide on their site. For this though, we just need the partition number, such as \/dev\/sda3 or \/dev\/hdb1. Now, make sure your superblock is the problem, by starting a filesystem check, replacing xxx with your partition name. Here, you can change ext4 to ext3, or ext2 to suit the filesystem. 1 sudo fsck.ext4 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_mi_skip_tracking":false,"ngg_post_thumbnail":0,"spay_email":"","jetpack_publicize_message":"","jetpack_is_tweetstorm":false,"jetpack_publicize_feature_enabled":true},"categories":[17,5,7],"tags":[],"aioseo_notices":[],"jetpack_featured_media_url":"","jetpack_publicize_connections":[],"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p5q9Zn-ca","jetpack-related-posts":[{"id":752,"url":"https:\/\/blog.box.kr\/?p=752","url_meta":{"origin":754,"position":0},"title":"Linux: Recover Corrupted Partition From A Bad Superblock","date":"2015-05-08","format":false,"excerpt":"Q.\u00a0How can I Recover a bad\u00a0superblock\u00a0from a corrupted ext3 partition to get back my data? I'm getting following error: \/dev\/sda2: Input\/output error mount: \/dev\/sda2: can't read superblock How do I fix this error? A.\u00a0Linux ext2\/3 filesystem\u00a0stores superblock at different backup location\u00a0so it is possible to get back data from corrupted\u2026","rel":"","context":"In "Linux"","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":662,"url":"https:\/\/blog.box.kr\/?p=662","url_meta":{"origin":754,"position":1},"title":"[Linux] disk mount","date":"2015-04-12","format":false,"excerpt":"mount \u2013t ext4 \/dev\/sdc1 \/desk mount \u2013t <\ud30c\uc77c\uc2dc\uc2a4\ud15c\ud615\uc2dd> <\ud30c\ud2f0\uc158\uba85> <\ub9c8\uc6b4\ud2b8\ud560\uc704\uce58> \u00a0 \ubd80\ud305\uc2dc\uc5d0 \uc790\ub3d9\uc73c\ub85c \ub9c8\uc6b4\ud2b8\ub97c \ub418\uac8c \ud558\uae30 \uc704\ud574\uc11c\ub294 \/etc\/fstab\u00a0\uc744 \uc218\uc815\ud574\ud568. Centos 6.3\ubd80\ud130\ub294 fstab \ub9c8\uc6b4\ud2b8\uc5d0 UUID\ub97c \uc774\uc6a9\ud558\uace0 \uc788\uc2b5\ub2c8\ub2e4. UUID\ub97c \ud655\uc778\ud558\uae30 \uc704\ud574\uc11c\ub294 blkid \uba85\ub839\uc5b4\ub97c \uc774\uc6a9\ud558\uac70\ub098 ls \u2013l \/dev\/disk\/by-uuid \ub97c \ud1b5\ud574\uc11c \ud655\uc778 \ud558\uc2e4 \uc218 \uc788\uc2b5\ub2c8\ub2e4. [root@localhost bin]# ls -lals \u2013l \/dev\/disk\/by-uuid ls: cannot access\u2026","rel":"","context":"In "\uae30\uc220\uc790\ub8cc"","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":660,"url":"https:\/\/blog.box.kr\/?p=660","url_meta":{"origin":754,"position":2},"title":"[Linux] \/dev\/sdc1 is apparently in use by the system; will not make a filesystem here!","date":"2015-04-12","format":false,"excerpt":"Centos \uc124\uce58 \ud558\uace0 HDD\ub97c \uc2e0\uaddc\ub85c INSTALL \ud560\ub54c fdisk \uae4c\uc9c0 \uc798 \ub410\ub294\ub370 \uc544\ub798\uc640 \uac19\uc740 \uc624\ub958 \ubc1c\uc0dd [root@localhost ~]# mkfs.ext4 \/dev\/sdb1 mke2fs 1.42.9 (28-Dec-2013) \/dev\/sdc1 is apparently in use by the system; will not make a filesystem here! \uc624\ub958 \ub0b4\uc6a9\uc744 \ubcf4\uba74 \ud574\ub2f9 \ub514\uc2a4\ud06c\uac00 \uc0ac\uc6a9\uc911\uc774\ub780\ub2e4.. \uc544.. ghost\uac00 \uc788\ub098? \uc5f4\uc2ec\ud788 \ucc3e\uc544 \ubcf8 \uacb0\uacfc\u00a0 Disk\u2026","rel":"","context":"In "\uae30\uc220\uc790\ub8cc"","img":{"alt_text":"","src":"","width":0,"height":0},"classes":[]},{"id":830,"url":"https:\/\/blog.box.kr\/?p=830","url_meta":{"origin":754,"position":3},"title":"[scrap]50 Most Frequently Used UNIX \/ Linux Commands (With Examples)","date":"2015-05-20","format":false,"excerpt":"http:\/\/www.thegeekstuff.com\/2010\/11\/50-linux-commands\/ \u00a0 This article provides practical examples for 50 most frequently used commands in Linux \/ UNIX. This is not a comprehensive list by any means, but this should give you a jumpstart on some of the common Linux commands. Bookmark this article for your future reference. 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