Linux 重新分配內存

一、目的

在使用CentOS6.3版本linux系統的時候，發現根目錄(/)的空間不是很充足，而其他目錄空間有很大的空閒，所以本文主要是針對現在已有的空間進行調整。首先，先來查看一下系統的空間分配情況：

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  

下面的詳細步驟部分將從vg_centos-lv_home分區下取出100G的空間添加到/vg_centos-lv_root分區上去。

二、詳細步驟

1、卸載vg_centos-lv_home分區

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

此時在用df命令查看將會發現/home目錄已經看不見了，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、從新設定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.  

這一步設定vg_home-lv_home大小沒有成功，系統提示我們先運行下面的命令，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  

從新設定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.  

檢查是否成功：

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、將lv_home邏輯分區減小到指定大小

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 /]#  

我認爲這個命令是將已經減少的100G空間拿到系統公共的區域，可以被其他分區加載和利用。
查詢卷組的信息：

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指定的應該是現在可在分配的空間。

4、增加vg_centos-lv_root分區的大小

將可用的空間添加到vg_centos-lv_root分區上面：

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 /]#  

從新設定該分區的大小：

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、再次查看分區大小

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  

我們發現vg_centos-lv_root分區的空間已經增加了125G，之所以比lv_home減少的空間要多25G主要是由於我們把系統所有的可用的空間都加在了lv_root分區。

三、所遇到的問題

1、在卸載/home目錄的時候失敗

可先執行如下fuser命令，然後再umount即可：

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

2、設定完lv_home的大小，再次mount該分區時，發現用df命令無法看到給分區，此時只要在mount一次即可

3、在設定lv_root的大小時，不要把Free PE / Size的空間全部都用上，這很可能會出現Free PE空間不足的現象，建議保留一點Free PE的空間。