[RHEL] 配置 LVM 卷
一、Introduction
基础预览 ：LVM 认知与扩容操作
高端实战：Linux系统如何迁移至LVM磁盘
之前转过一篇文章 LVM分区在线扩容 ，其原因是我需要给公司的 LVM 卷进行一个扩展卷的扩大。
那其实，不仅只有扩大。还有：缩小以及修复。
二、Environment
[root@server0 ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 253:0 0 10G 0 disk
└─vda1 253:1 0 10G 0 part /
vdb 253:16 0 10G 0 disk
└─vdb1 253:17 0 512M 0 part
└─finance-loans 252:0 0 256M 0 lvm /finance/loans
注释：可以看到系统内已经有了一个 LVM 卷了，但系统还有剩余空间（9.5G）还未被使用。
Firest：Format File System
...
Command (m for help): p
Disk /dev/vdb: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0009f6d4
Device Boot Start End Blocks Id System
/dev/vdb1 2048 1050623 524288 8e Linux LVM
**提示： **上述具体 Command 解释，位于文章底部有附录—— Command_action
**注意： **the next reboot or after you run partprobe(8) or kpartx(8)
Second：Create Physical Volume
[root@server0 ~]# pvcreate /dev/vdb2
Third： Create Volume Group
[root@server0 ~]# vgcreate vg /dev/vdb2
Volume group "vg" successfully created
BTW： " -s" 可定义 PEnum 块大小；
Finished：Make Volume Group join LVM
[root@server0 ~]# lvcreate -n lvm vg -L 100M
Logical volume "lvm" created
BTW： "-l" 可定义 PEnum 数量
**注意： ** " -L " 可使用 +size|-size|size(means equal)
三、Expand Space
1、单盘扩大
[root@server0 ~]# lvextend -L +100M /dev/vg/lvm --resizefs
fsck from util-linux 2.23.2
/dev/mapper/vg-lvm: clean, 11/25688 files, 8896/102400 blocks
Extending logical volume lvm to 200.00 MiB
Logical volume lvm successfully resized
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/mapper/vg-lvm to 204800 (1k) blocks.
The filesystem on /dev/mapper/vg-lvm is now 204800 blocks long.
注意：我这里偷了一个懒把俩条命令结合在一起了，否则 lvs /path/to/lvm 空间大小是不会立即生效的。
Q1：fsadm: Cannot get FSTYPE of "/dev/vg/lvm" Filesystem check failed.
A1：please format Filesystem promptly.
Q2：Forgot to add option "--resizefs"
A2：redo or ext2/ext3/ext4 filesystem to execute resizefs /path/to/lvm , but xfs filesystem must to be execute xfs_growfs mountpoint . The difference is looking what's command admin execute mkfs.ext4 or mkfs.xfs. Attention：XFS must to use mountpoint or not to use /path/to/lvm
2、加磁盘扩大
fdisk /dev/disk
new
default
size
type
choose
82
print
write
pvcreate /path/to/new/create/lvm_disk
vgcreate <vg_name> /path/to/new/crate/lvm_disk
提示：其他一样。
四、Reduce Space
[root@server0 ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 253:0 0 10G 0 disk
└─vda1 253:1 0 10G 0 part /
vdb 253:16 0 10G 0 disk
├─vdb1 253:17 0 512M 0 part
│ └─finance-loans 252:0 0 256M 0 lvm /finance/loans
└─vdb2 253:18 0 1G 0 part
└─vg-lvm 252:1 0 200M 0 lvm
Firest：unmount device
[root@server0 ~]# umount /dev/vg/lvm
Second：check a Linux ext2/ext3/ext4 file system
[root@server0 ~]# e2fsck -f /dev/vg/lvm
e2fsck 1.42.9 (28-Dec-2013)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/vg/lvm: 11/49400 files (9.1% non-contiguous), 11884/204800 blocks
Third：resize umount and e2fsck device
[root@server0 ~]# resize2fs /dev/vg/lvm 66M
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/vg/lvm to 67584 (1k) blocks.
The filesystem on /dev/vg/lvm is now 67584 blocks long.
提示：当需要进行 LVM 缩小操作时，所有操作必须相反。所以该步异常重要，下一步需要使 RHEL 重新识别被缩小的 LVM 卷。
Finished：reduce device
[root@server0 ~]# lvreduce -L 60M /dev/vg/lvm
WARNING: Reducing active logical volume to 60.00 MiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lvm? [y/n]: y
Reducing logical volume lvm to 60.00 MiB
Logical volume lvm successfully resized
[root@server0 ~]# vgs vg
VG #PV #LV #SN Attr VSize VFree
vg 1 1 0 wz--n- 1020.00m 960.00m
[root@server0 ~]# lvs vg
LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert
lvm vg -wi-a----- 60.00m
Q：why the output tell me that "Rounding size to boundary between physical extents"
A：the lvm have the boundary and the defaults PE size was 4MB. You can change them with lvchange -s {1..4} <vgname> and check it with vgdisplay <vgname>.
五、Restore Destroyed LVM
Firest：Check LVM devices
[root@server0 ~]# vgcfgrestore -l vg
File: /etc/lvm/archive/vg_00033-587950815.vg
VG name: vg
Description: Created *before* executing 'vgscan'
Backup Time: Sun Nov 5 23:28:28 2017
File: /etc/lvm/archive/vg_00034-1362264111.vg
VG name: vg
Description: Created *before* executing 'vgscan'
Backup Time: Sun Nov 5 23:28:28 2017
File: /etc/lvm/backup/vg
VG name: vg
Description: Created *after* executing 'vgscan'
Backup Time: Sun Nov 5 23:28:28 2017
Second：Restore
vgcfgrestore -f <file_list_print> <vg>
Exameple: vgcfgrestore -f /etc/lvm/archive/vg_00034-1362264111.vg vg
Finished：unActive and Active
lvchange -an /dev/<vg>/<lvm>
lvchange -ay /dev/<vg>/<lvm>
Others
Command (m for help): m
Command action
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition
g create a new empty GPT partition table
G create an IRIX (SGI) partition table
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition's system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality (experts only)