今天在安装oracle 11 rac的时候，查看操作系统df -lh,发现/home目录竟然分了500多G，/根目录才有50G，当时我就爆了句粗口，这TM系统是怎么做的。
Filesystem                              Size     Used    Avail   Use% Mounted on
/dev/mapper/vg_db5-lv_root                 50G     6.2G   41G   14%    /
tmpfs                                      127G    84K  127G    1%     /dev/shm
/dev/sdq1                                  477M    37M  415M    9%     /boot
/dev/mapper/vg_db5-lv_home                 496G    70M  471G    1%     /home

#vgdisplay
--- Volume group ---
  VG Name               vg_db5
  System ID            
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  4
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               557.26 GiB
  PE Size               4.00 MiB
  Total PE              142658
  Alloc PE / Size       142658 / 557.26 GiB
  Free  PE / Size       0 / 0  
  VG UUID               plc2K9-lRVy-bcck-B9Qp-3F8k-H6cW-W4vRdS


#lvdisplay
--- Logical volume ---
  LV Path                /dev/vg_db6/lv_root
  LV Name                lv_root
  VG Name                vg_db6
  LV UUID                6HlVnp-6RGm-kORQ-eOx6-nQQV-8PWB-Gg4WNE
  LV Write Access        read/write
  LV Creation host, time db6, 2015-02-02 19:25:11 +0800
  LV Status              available
  # open                 1
  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/vg_db6/lv_home
  LV Name                lv_home
  VG Name                vg_db6
  LV UUID                yuBJai-96D6-JFwX-cmXR-EeXE-cUuU-uqRl3l
  LV Write Access        read/write
  LV Creation host, time db6, 2015-02-02 19:25:17 +0800
  LV Status              available
  # open                 1
  LV Size                503.26 GiB
  Current LE             128834
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:10
  
  --- Logical volume ---
  LV Path                /dev/vg_db6/lv_swap
  LV Name                lv_swap
  VG Name                vg_db6
  LV UUID                d5FqB1-tTHM-HSrb-b0tm-r1Ms-XnvP-dH5ovs
  LV Write Access        read/write
  LV Creation host, time db6, 2015-02-02 19:27:23 +0800
  LV Status              available
  # open                 1
  LV Size                4.00 GiB
  Current LE             1024
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:1

有三个lv在一个VG里，决定把这三个LV的大小给调整一下。把lv_home调小,然后把lv_root调大。注意，缩小空间是有风险的，所以我先把里面的oracle,grid用户还有所有的组都删除了，然后重启系统。
#userdel oracle
#userdel grid
#groudel  oinstall
....................
重启之后，查看/etc/group,/etc/passwd,确认没有用户和组了，我们就可以开始了。
1.#umount /home1.#umount /home

如果不成功，可能会报错，解决方法如下：umount: /mnt/cdrom: device is busy.
 (In some cases useful info about processes that
use the device is found by lsof(8) or user(1))

#umount /mnt/cdrom/ -f    //强制卸载也不行

umount2: 设备或资源忙

umount: /mnt: device is busy.

(In some cases useful info about processes that use

the device is found by lsof(8) or fuser(1))umount2: 设备或资源忙