解决硬盘挂载报错：
mount: unknown filesystem type 'LVM2_member'
mount: you must specify the filesystem type
情况说明：
客户托管的服务器到机房，系统是Linux，无法启动，只能做系统恢复。询问后得知：
- 数据盘有数据。无法全格。
- 客户是小白，对Linux一点不懂。（既不懂如何管理）?
我的解决思路（保险起见）：
上一块500G新硬盘，做上linux系统。将先前那块磁盘挂上去，之后拷贝数据。
下面开始。
查看磁盘情况：
[root@renwole-com ~]# fdisk -l Disk /dev/sda: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x000a9411 Device Boot Start End Blocks Id System /dev/sda1 * 1 26 204800 83 Linux Partition 1 does not end on cylinder boundary. /dev/sda2 26 6553 52428800 83 Linux /dev/sda3 6553 7075 4194304 82 Linux swap / Solaris /dev/sda4 7075 60802 431557656 5 Extended /dev/sda5 7076 60802 431556608 83 Linux Disk /dev/sdb: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0xa154a154 Device Boot Start End Blocks Id System /dev/sdb1 * 1 64 512000 83 Linux Partition 1 does not end on cylinder boundary. /dev/sdb2 64 60802 487873536 8e Linux LVM Disk /dev/mapper/VolGroup-lv_root: 53.7 GB, 53687091200 bytes 255 heads, 63 sectors/track, 6527 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 Disk /dev/mapper/VolGroup-lv_home: 441.8 GB, 441765068800 bytes 255 heads, 63 sectors/track, 53708 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000 ...
说明：红色部分是以前系统坏的老盘。
安装 lvm2：
[root@renwole-com ~]# yum install lvm2 -y
查看物理卷：
[root@renwole-com ~]# pvs PV VG Fmt Attr PSize PFree /dev/sdb2 VolGroup lvm2 a--u 465.27g 0
查看卷组：
[root@renwole-com ~]# lvdisplay --- Logical volume --- LV Path /dev/VolGroup/lv_root LV Name lv_root VG Name VolGroup LV UUID 3Y5UYD-x0H9-F25h-foUz-rm0O-cgzl-pE8FbF LV Write Access read/write LV Creation host, time localhost.localdomain, 2015-07-20 17:29:35 +0800 LV Status available # open 0 LV Size 50.00 GiB Current LE 12800 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:0 --- Logical volume --- LV Path /dev/VolGroup/lv_home LV Name lv_home VG Name VolGroup LV UUID Eu7UKx-LPkM-RDQ6-ACym-KOOW-t2RC-oVq0Zn LV Write Access read/write LV Creation host, time localhost.localdomain, 2015-07-20 17:29:56 +0800 LV Status available # open 1 LV Size 411.43 GiB Current LE 105325 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:1 --- Logical volume --- LV Path /dev/VolGroup/lv_swap LV Name lv_swap VG Name VolGroup LV UUID PBkdrg-lhsO-vkde-RvC0-ryUh-p0pf-aMnBds LV Write Access read/write LV Creation host, time localhost.localdomain, 2015-07-20 17:32:40 +0800 LV Status available # open 0 LV Size 3.84 GiB Current LE 984 Segments 1 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:2
激活卷组：
[root@renwole-com ~]# vgchange -ay /dev/VolGroup 3 logical volume(s) in volume group "VolGroup" now active
挂载硬盘：
[root@renwole-com ~]# mount /dev/VolGroup/lv_home /apps/
/apps是我新建的目录。
查看挂载情况：
[root@renwole-com ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/sda2 50G 2.1G 45G 5% / tmpfs 3.9G 0 3.9G 0% /dev/shm /dev/sda1 194M 34M 151M 19% /boot /dev/sda5 406G 199M 385G 1% /home /dev/mapper/VolGroup-lv_home 405G 199M 385G 1% /apps
进入apps目录一看，哇；数据还在，可喜可贺呀。
另外：如果挂载报错：
mount: you must specify the filesystem type
可以使用以下方法查看磁盘格式类型，然后加参数 -t 指定格式挂载即可。
[root@renwole-com ~]# file -s /dev/sda1 /dev/sda1: Linux rev 1.0 ext4 filesystem data (needs journal recovery) (extents) (huge files)
重要说明：
未找到合适的解决方案前，切勿对硬盘删分区，否则会损坏数据。
即便挂载成功，切勿使用mv或rm命令，请使用cp命令。
特别注意：在Linux下，若使用软件恢复数据，几乎是不现实的。