在安装Linux系统时LVM划分/分区过大，使用一段时间后觉得没必要把/分区（/dev/vgsrv/root)分的这么大（100G呢），此时可以从Linux安装光盘启动进入rescue模式,选择相关的语言，键盘模式，当系统提示启用网络设备时，选择“NO”，然后在提示允许rescue模式挂载本地Linux系统到/mnt/sysimage下时选择“Skip”，文件系统必须不被挂载才可以对/分区减小容量操作。最后系统会提示选择进入shell终端还是reboot机器，选择进入shell终端。
依次输入pvscan、vgscan、lvscan三个命令扫描pv、vg、lv相关信息，
然后输入 lvchange -ay /dev/vgsrv/root（上文提到的/分区名称）此命令是激活/分区所在的逻辑卷。
下一步是缩小文件系统大小和逻辑卷/dev/vgsrv/root，
在缩小文件系统前先检查下硬盘，e2fsck -f /dev/vgsrv/root
缩小文件系统为指定大小: resize2fs/dev/vgsrv/root 50G
设置逻辑卷大小为50G：lvreduce -L 50g /dev/vgsrv/root
系统会进入是否缩小逻辑卷，输入 y 确定。
再检查下硬盘，e2fsck -f /dev/vgsrv/root
缩小逻辑卷成功后可输入vgdisplay，lvdisplay查看。输入exit可退出rescue模式。
正常进入系统后, 下面针对系统Swap分区扩容与缩减做说明：
[root@server10 ~]# free -g
total used free shared buffers cached
Mem: 62 62 0 0 0 60
-/+ buffers/cache: 2 60
Swap: 127 0 127
[root@server10 ~]# df -h
[root@server10 ~]# cat /etc/fstab
/dev/VolGroup00/LogVol01 swap swap defaults 0 0
[root@server10 ~]# lvdisplay
— Logical volume —
LV Name /dev/VolGroup00/LogVol00
VG Name VolGroup00
LV UUID oZ7rEm-hphT-MsGk-fNaD-RC5X-INgZ-oCJdml
LV Write Access read/write
LV Status available
# open 1
LV Size 150.84 GB
Current LE 4827
Segments 1
Allocation inherit
Read ahead sectors auto
– currently set to 256
Block device 253:0
— Logical volume —
LV Name /dev/VolGroup00/LogVol01
VG Name VolGroup00
LV UUID pCpqVB-cwXV-MunF-OtBQ-usYA-hFxt-l07IJc
LV Write Access read/write
LV Status available
# open 1
LV Size 127.91 GB
Current LE 4093
Segments 1
Allocation inherit
Read ahead sectors auto
– currently set to 256
Block device 253:1
[root@server10 ~]# vgdisplay
— Volume group —
VG Name VolGroup00
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 3
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 1
Act PV 1
VG Size 278.75 GB
PE Size 32.00 MB
Total PE 8920
Alloc PE / Size 8920 / 278.75 GB
Free PE / Size 0 / 0
VG UUID 9hHRZZ-VUd4-bMwc-rnhK-wiyq-sPZw-dtJREo
[root@server10 ~]# free -m
total used free shared buffers cached
Mem: 64449 64129 320 0 327 61494
-/+ buffers/cache: 2307 62142
Swap: 130975 0 130975
[root@server10 ~]# swapoff -a
[root@server10 ~]# free -m
total used free shared buffers cached
Mem: 64449 64065 384 0 327 61494
-/+ buffers/cache: 2243 62206
Swap: 0 0 0
[root@server10 ~]# lvreduce /dev/VolGroup00/LogVol01 -L -64G
WARNING: Reducing active logical volume to 63.91 GB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce LogVol01? [y/n]: y
Reducing logical volume LogVol01 to 63.91 GB
Logical volume LogVol01 successfully resized
[root@server10 ~]# mkswap /dev/VolGroup00/LogVol01
Setting up swapspace version 1, size = 68618809 kB
[root@server10 ~]# swapon /dev/VolGroup00/LogVol01
[root@server10 ~]# free -m
total used free shared buffers cached
Mem: 64449 64150 299 0 327 61549
-/+ buffers/cache: 2273 62175
Swap: 65439 0 65439
[root@server10 ~]# free -g
total used free shared buffers cached
Mem: 62 62 0 0 0 60
-/+ buffers/cache: 2 60
Swap: 63 0 63
[root@server10 ~]# vgdisplay
— Volume group —
VG Name VolGroup00
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 4
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 1
Act PV 1
VG Size 278.75 GB
PE Size 32.00 MB
Total PE 8920
Alloc PE / Size 6872 / 214.75 GB
Free PE / Size 2048 / 64.00 GB
VG UUID 9hHRZZ-VUd4-bMwc-rnhK-wiyq-sPZw-dtJREo
[root@server10 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
147G 74G 65G 54% /
/dev/sda1 99M 13M 81M 14% /boot
tmpfs 32G 0 32G 0% /dev/shm
[root@server10 ~]# mount
/dev/mapper/VolGroup00-LogVol00 on / type ext3 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
/dev/sda1 on /boot type ext3 (rw)
tmpfs on /dev/shm type tmpfs (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
[root@server10 ~]# lvextend /dev/VolGroup00/LogVol00 -l +100%FREE
Extending logical volume LogVol00 to 214.84 GB
Logical volume LogVol00 successfully resized
[root@server10 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
147G 74G 65G 54% /
/dev/sda1 99M 13M 81M 14% /boot
tmpfs 32G 0 32G 0% /dev/shm
[root@server10 ~]# resize2fs /dev/VolGroup00/LogVol00
resize2fs 1.39 (29-May-2006)
Filesystem at /dev/VolGroup00/LogVol00 is mounted on /; on-line resizing required
Performing an on-line resize of /dev/VolGroup00/LogVol00 to 56320000 (4k) blocks.
The filesystem on /dev/VolGroup00/LogVol00 is now 56320000 blocks long.
[root@server10 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
209G 74G 124G 38% /
/dev/sda1 99M 13M 81M 14% /boot
tmpfs 32G 0 32G 0% /dev/shm
[root@server10 ~]#
以上是减容量，下面针对增加容量做一下命令解析：
swapoff -a //关闭swap分区
lvextend -l +100%free /dev/VolGroup00/LogVol00 //增加swap卷所有可用空间
mkswap /dev/VolGroup00/LogVol00 //建立swap分区
swapon /dev/VolGroup00/LogVol00//启用swap分区
