问题描述
虚拟机异常下电，重新开机后其中一个磁盘的一个分区只有1KiB
处理步骤
1、执行lsblk查看分区情况，显示只有1kb
[root@test ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 30G 0 disk
├─sda1 8:1 0 600M 0 part /boot/efi
├─sda2 8:2 0 1G 0 part /boot
└─sda3 8:3 0 28.4G 0 part
├─cs-root 253:0 0 25.4G 0 lvm /
└─cs-swap 253:1 0 3G 0 lvm [SWAP]
sdb 8:16 0 500G 0 disk
├─sdb1 8:17 0 20G 0 part
└─sdb2 8:18 0 1K 0 part 2、执行tune2fs查询分区详细信息，提示无法打开分区有超级坏块
[root@test ~]# tune2fs -l /dev/sdb2
tune2fs 1.45.6 (20-Mar-2020)
tune2fs: Attempt to read block from filesystem resulted in short read while trying to open /dev/sdb2
Couldn't find valid filesystem superblock.
3、执行 make2fs -n 尝试查询备用超级块，依旧提示失败
[root@test ~]# mke2fs -n /dev/sdb2
mke2fs 1.45.6 (20-Mar-2020)
Found a dos partition table in /dev/sdb2
Proceed anyway? (y,N) y
mke2fs: inode_size (128) * inodes_count (0) too big for a
filesystem with 0 blocks, specify higher inode_ratio (-i)
or lower inode count (-N).4、使用fdisk查看分区表看总体是正常的，但针对单分区是异常的
[root@test ~]# fdisk -l /dev/sdb
Disk /dev/sdb: 500 GiB, 536870912000 bytes, 1048576000 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x6b9fc1d1
Device Boot Start End Sectors Size Id Type
/dev/sdb1 2048 41945087 41943040 20G 83 Linux
/dev/sdb2 41945088 1048575999 1006630912 480G 83 Linux
[root@test ~]# fdisk -l /dev/sdb1
Disk /dev/sdb1: 20 GiB, 21474836480 bytes, 41943040 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
[root@test ~]# fdisk -l /dev/sdb2
Disk /dev/sdb2: 1 KiB, 1024 bytes, 2 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x00000000
5、经过上述步骤查询判断为整块磁盘的前512字节分区表丢失一小部分数据，刚好丢失的数据是在sdb2分区表中，备份磁盘后尝试使用分区工具重新分区
[root@test ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.32.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): p
Disk /dev/sdb: 500 GiB, 536870912000 bytes, 1048576000 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x6b9fc1d1
Device Boot Start End Sectors Size Id Type
/dev/sdb1 2048 41945087 41943040 20G 83 Linux
/dev/sdb2 41945088 1048575999 1006630912 480G 83 Linux
Command (m for help): d
Partition number (1,2, default 2): 2
Partition 2 has been deleted.
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
=======================↑删除分区后保存再重新创建
[root@test ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.32.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): n
Partition type
p primary (1 primary, 0 extended, 3 free)
e extended (container for logical partitions)
Select (default p): e
Partition number (2-4, default 2): 2
First sector (41945088-1048575999, default 41945088):41945088
Last sector, +sectors or +size{K,M,G,T,P} (41945088-1048575999, default 1048575999):
Created a new partition 2 of type 'Extended' and of size 480 GiB.
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
=======================注意不用格式化6、尝试挂载
[root@test ~]# mount /dev/sdb2 /mnt
成功没有报错问题复现
经过问题得处理基本上确定是分区表丢失了一部分关于sdb2的分区表信息，所以比较好浮现，直接使用dd命令将分区前512字节抹除一小段数据
#dd if=/dev/zero of=/dev/sdb bs=1 skip=420 count=92
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