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CentOS下lv调整空间大小

2017年10月20日

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：

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[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

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

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[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  
 
[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. 
 
[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 /]#  
 
[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 /]#

查看一下lv目前的情况

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[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：

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[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 /]#  
 
[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

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[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：

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[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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