转自：http://blog.csdn.net/andy_yf/article/details/7831482

一、目的

在使用CentOS6.3版本linux系统的时候，发现根目录(/)的空间不是很充足，而其他目录空间有很大的空闲，所以本文主要是针对现在已有的空间进行调整。首先，先来查看一下系统的空间分配情况：

[root@CentOS-78 /]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_centos-lv_root
                       50G   14G   34G  30% /
tmpfs                 1.9G     0  1.9G   0% /dev/shm
/dev/sda1             485M   37M  423M   8% /boot
/dev/mapper/vg_centos-lv_home
                      404G  670M  382G   1% /home

下面的详细步骤部分将从vg_centos-lv_home分区下取出100G的空间添加到/vg_centos-lv_root分区上去。

二、详细步骤

1、卸载vg_centos-lv_home分区

[root@CentOS-78 /]# umount /home

此时在用df命令查看将会发现/home目录已经看不见了，如下所示：

[root@CentOS-78 /]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_centos-lv_root
                       50G   14G   34G  30% /
tmpfs                 1.9G     0  1.9G   0% /dev/shm
/dev/sda1             485M   37M  423M   8% /boot

2、从新设定vg_home-lv_home的大小

[root@CentOS-78 /]# resize2fs -p /dev/mapper/vg_centos-lv_home 282G
resize2fs 1.41.12 (17-May-2010)
Please run 'e2fsck -f /dev/mapper/vg_centos-lv_home' first.

这一步设定vg_home-lv_home大小没有成功，系统提示我们先运行下面的命令，操作如下：

[root@CentOS-78 /]# e2fsck -f /dev/mapper/vg_centos-lv_home
e2fsck 1.41.12 (17-May-2010)
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/mapper/vg_centos-lv_home: 1386/26836992 files (0.9% non-contiguous), 1855856/107344896 blocks

从新设定vg_home-lv_home的大小：

[root@CentOS-78 /]# resize2fs -p /dev/mapper/vg_centos-lv_home 282G
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/mapper/vg_centos-lv_home to 73924608 (4k) blocks.
Begin pass 2 (max = 43)
Relocating blocks             XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Begin pass 3 (max = 3276)
Scanning inode table          XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
Begin pass 4 (max = 266)
Updating inode references     XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
The filesystem on /dev/mapper/vg_centos-lv_home is now 73924608 blocks long.

检查是否成功：

[root@CentOS-78 /]# mount /home
[root@CentOS-78 /]#
[root@CentOS-78 /]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_centos-lv_root
                       50G   14G   34G  30% /
tmpfs                 1.9G     0  1.9G   0% /dev/shm
/dev/sda1             485M   37M  423M   8% /boot
/dev/mapper/vg_centos-lv_home
                      278G  663M  263G   1% /home
[root@CentOS-78 /]#

3、将lv_home逻辑分区减小到指定大小

[root@CentOS-78 /]# lvreduce -L 282G /dev/mapper/vg_centos-lv_home
  WARNING: Reducing active and open logical volume to 282.00 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lv_home? [y/n]: y
  Reducing logical volume lv_home to 282.00 GiB
  Logical volume lv_home successfully resized
[root@CentOS-78 /]#

我认为这个命令是将已经减少的100G空间拿到系统公共的区域，可以被其他分区加载和利用。

查询卷组的信息：

[root@CentOS-78 /]# vgdisplay
  --- Volume group ---
  VG Name               vg_centos
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  5
  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               465.27 GiB
  PE Size               4.00 MiB
  Total PE              119109
  Alloc PE / Size       86472 / 337.78 GiB
  Free  PE / Size       32637 / 127.49 GiB
  VG UUID               1k4ooN-RFV9-uyf1-uMYf-aERG-YaGs-ZNoSD6

Free PE / Size指定的应该是现在可在分配的空间。

4、增加vg_centos-lv_root分区的大小

将可用的空间添加到vg_centos-lv_root分区上面：

[root@CentOS-78 /]# lvextend -L +127.40G /dev/mapper/vg_centos-lv_root
  Rounding up size to full physical extent 127.40 GiB
  Extending logical volume lv_root to 177.40 GiB
  Logical volume lv_root successfully resized
[root@CentOS-78 /]#

从新设定该分区的大小：

[root@CentOS-78 /]# resize2fs -p /dev/mapper/vg_centos-lv_root
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/mapper/vg_centos-lv_root is mounted on /; on-line resizing required
old desc_blocks = 4, new_desc_blocks = 12
Performing an on-line resize of /dev/mapper/vg_centos-lv_root to 46504960 (4k) blocks.
The filesystem on /dev/mapper/vg_centos-lv_root is now 46504960 blocks long.

5、再次查看分区大小

[root@CentOS-78 /]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_centos-lv_root
                      175G   14G  153G   9% /
tmpfs                 1.9G     0  1.9G   0% /dev/shm
/dev/sda1             485M   37M  423M   8% /boot
/dev/mapper/vg_centos-lv_home
                      278G  663M  263G   1% /home

我们发现vg_centos-lv_root分区的空间已经增加了125G，之所以比lv_home减少的空间要多25G主要是由于我们把系统所有的可用的空间都加在了lv_root分区。

三、所遇到的问题

1、在卸载/home目录的时候失败

可先执行如下fuser命令，然后再umount即可：

[root@CentOS-78 /]# fuser -m /home
[root@CentOS-78 /]#

2、设定完lv_home的大小，再次mount该分区时，发现用df命令无法看到给分区，此时只要在mount一次即可

3、在设定lv_root的大小时，不要把Free PE / Size的空间全部都用上，这很可能会出现Free PE空间不足的现象，建议保留一点Free PE的空间。

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参考：

http://hi.baidu.com/%B7%E7%B6%C0/blog/item/c4aa9a81b204dbc89023d956.html

http://qianxunniao.iteye.com/blog/1393726