硬盘 mount (挂载)出现 superblock (超级块)

本文介绍了当 linux 系统下硬盘挂在出现 superblock 错误的解决方法

## 现象

`$sudo mount -t ext4 /dev/sdb1 /mnt/media`

mount: wrong fs type, bad option, bad superblock on /dev/sdb1,
    missing codepage or helper program, or other error
    In some cases useful info is found in syslog - try
    dmesg | tail or so

`$dmesg | tail -n 20`

[ 662.775753] EXT4-fs (sdb1): error loading journal
    [ 664.141542] sdb: sdb1
    [ 665.520490] JBD2: Invalid checksum recovering block 129 in log
    [ 666.650534] JBD2: recovery failed
    [ 666.650545] EXT4-fs (sdb1): error loading journal
    [ 885.576328] sdb: sdb1
    [ 886.927562] JBD2: Invalid checksum recovering block 129 in log
    [ 888.148915] JBD2: recovery failed
    [ 888.148925] EXT4-fs (sdb1): error loading journal
    [ 1351.768797] sdb: sdb1
    [ 1353.130971] JBD2: Invalid checksum recovering block 129 in log
    [ 1354.269588] JBD2: recovery failed
    [ 1354.269598] EXT4-fs (sdb1): error loading journal
    [ 1714.130574] sdb: sdb1
    [ 1715.538450] JBD2: Invalid checksum recovering block 129 in log
    [ 1716.661510] JBD2: recovery failed
    [ 1716.661521] EXT4-fs (sdb1): error loading journal
    [ 2052.229550] JBD2: Invalid checksum recovering block 129 in log
    [ 2053.363165] JBD2: recovery failed
    [ 2053.363176] EXT4-fs (sdb1): error loading journal

## 修复过程
`$fdisk -l` 查看硬盘情况

* 修复分区表

`$testdisk`

=>选择 [Create]
=>选择 /dev/sdb
=>选择 EFI GPT #选择原分区表类型
=>选择 Analyse #进行分析
=>列出分区, 按P进入可查看文件
=>按"w"写入分区
=>一路退出程序后重启
=>ok

看到 `/dev/sdb1` 是 `Microsoft basic data` 分区, 但原分区是 `ext4`

* 转换分区表格式

`$fdisk /dev/sdb` gdisk是否是操作GPT的唯一,而fdisk只能是MBR?

=>输入`t`
=>输入`15` #转换 `Microsoft basic data` 到 `linux filesystem`(编号15)
=>输入 `w` # 保存修改

* 使用e2fsck修复superblock

`$./e2fsck -a /dev/sdb1`

Journal checksum error found in /dev/sdb1
	/dev/sdb1 was not cleanly unmounted, 强制检查.
	/dev/sdb1: 5205/183148544 files (2.9% non-contiguous), 270824019/732566385 blocks

※如果出现: $e2fsck: Get a newer version of e2fsck! 时需要下载最新的e2fsck

如果不行可使用备份超级块方法

* 查找超级块

$testdisk->[Create]->[/dev/sdv/]->[EFi GPT]->[Advanced] #根据原分区类型选择
如果出现 `$> 1 P Unknown 2048 5860533127 5860531080`

则选择 [Type]->[EFI System]->[ext4] #根据原分区类型选择
    superblock 0, blocksize=4096 []
    superblock 32768, blocksize=4096 []
    superblock 98304, blocksize=4096 []
    superblock 163840, blocksize=4096 []
    superblock 229376, blocksize=4096 []
    superblock 294912, blocksize=4096 []
    superblock 819200, blocksize=4096 []
    superblock 884736, blocksize=4096 []
    superblock 1605632, blocksize=4096 []
    superblock 2654208, blocksize=4096 []

`$e2fsck -b 32768 /dev/sdb1` 使用备份修复

如果失败可重复尝试其他超级块

### 参考
* [修复损坏的 ext4 大分区数据](http://exaos.github.io/blog/2013/03/05_fix-bad-ext4.html)
* [记一次 superblock 损坏导致服务器无法启动的故障修复](http://www.cppblog.com/dancefire/archive/2011/03/09/fix-bad-superblock-in-linux.html)
* [ext4 broken file system on ubuntu 14.04.4](https://askubuntu.com/questions/747656/ext4-broken-file-system-on-ubuntu-14-04-4)
* [linux下的分区修复软件Testdisk](http://www.php-oa.com/2009/02/13/testdisk.html)

硬盘 mount (挂载)出现 superblock (超级块)

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