Linux 重新分配内存

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：

01.[root@CentOS-78 /]# df -h  
02.Filesystem            Size  Used Avail Use% Mounted on  
03./dev/mapper/vg_centos-lv_root  
04.                       50G   14G   34G  30% /  
05.tmpfs                 1.9G     0  1.9G   0% /dev/shm  
06./dev/sda1             485M   37M  423M   8% /boot  
07./dev/mapper/vg_centos-lv_home  
08.                      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

01.[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：

01.[root@CentOS-78 /]# df -h  
02.Filesystem            Size  Used Avail Use% Mounted on  
03./dev/mapper/vg_centos-lv_root  
04.                       50G   14G   34G  30% /  
05.tmpfs                 1.9G     0  1.9G   0% /dev/shm  
06./dev/sda1             485M   37M  423M   8% /boot  

2、从新设定vg_home-lv_home的大小

01.[root@CentOS-78 /]# resize2fs -p /dev/mapper/vg_centos-lv_home 282G  
02.resize2fs 1.41.12 (17-May-2010)  
03.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：

01.[root@CentOS-78 /]# e2fsck -f /dev/mapper/vg_centos-lv_home  
02.e2fsck 1.41.12 (17-May-2010)  
03.Pass 1: Checking inodes, blocks, and sizes  
04.Pass 2: Checking directory structure  
05.Pass 3: Checking directory connectivity  
06.Pass 4: Checking reference counts  
07.Pass 5: Checking group summary information  
08./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：

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

检查是否成功：

01.[root@CentOS-78 /]# mount /home  
02.[root@CentOS-78 /]#  
03.[root@CentOS-78 /]# df -h  
04.Filesystem            Size  Used Avail Use% Mounted on  
05./dev/mapper/vg_centos-lv_root  
06.                       50G   14G   34G  30% /  
07.tmpfs                 1.9G     0  1.9G   0% /dev/shm  
08./dev/sda1             485M   37M  423M   8% /boot  
09./dev/mapper/vg_centos-lv_home  
10.                      278G  663M  263G   1% /home  
11.[root@CentOS-78 /]#  

3、将lv_home逻辑分区减小到指定大小

01.[root@CentOS-78 /]# lvreduce -L 282G /dev/mapper/vg_centos-lv_home  
02.  WARNING: Reducing active and open logical volume to 282.00 GiB  
03.  THIS MAY DESTROY YOUR DATA (filesystem etc.)  
04.Do you really want to reduce lv_home? [y/n]: y  
05.  Reducing logical volume lv_home to 282.00 GiB  
06.  Logical volume lv_home successfully resized  
07.[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：

01.[root@CentOS-78 /]# vgdisplay  
02.  --- Volume group ---  
03.  VG Name               vg_centos  
04.  System ID  
05.  Format                lvm2  
06.  Metadata Areas        1  
07.  Metadata Sequence No  5  
08.  VG Access             read/write  
09.  VG Status             resizable  
10.  MAX LV                0  
11.  Cur LV                3  
12.  Open LV               3  
13.  Max PV                0  
14.  Cur PV                1  
15.  Act PV                1  
16.  VG Size               465.27 GiB  
17.  PE Size               4.00 MiB  
18.  Total PE              119109  
19.  Alloc PE / Size       86472 / 337.78 GiB  
20.  Free  PE / Size       32637 / 127.49 GiB  
21.  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：

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

从新设定该分区的大小：

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

5、再次查看分区大小

01.[root@CentOS-78 /]# df -h  
02.Filesystem            Size  Used Avail Use% Mounted on  
03./dev/mapper/vg_centos-lv_root  
04.                      175G   14G  153G   9% /  
05.tmpfs                 1.9G     0  1.9G   0% /dev/shm  
06./dev/sda1             485M   37M  423M   8% /boot  
07./dev/mapper/vg_centos-lv_home  
08.                      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：

01.[root@CentOS-78 /]# fuser -m /home  
02.[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。