LVM 管理减少swap分区空间增加到根分区

简介

LVM是 Logical Volume Manager（逻辑卷管理）的简写，它是Linux环境下对磁盘分区进行管理的一种机制，它由Heinz Mauelshagen在Linux 2.4内核上实现。

物理存储介质（PhysicalStorageMedia）

指系统的物理存储设备：磁盘，如：/dev/hda、/dev/sda等，是存储系统最底层的存储单元。

物理卷（Physical Volume，PV）

指磁盘分区或从逻辑上与磁盘分区具有同样功能的设备（如RAID），是LVM的基本存储逻辑块，但和基本的物理存储介质（如分区、磁盘等）比较，却包含有与LVM相关的管理参数。

卷组（Volume Group，VG）

类似于非LVM系统中的物理磁盘，其由一个或多个物理卷PV组成。可以在卷组上创建一个或多个LV（逻辑卷）。

逻辑卷（Logical Volume，LV）

类似于非LVM系统中的磁盘分区，逻辑卷建立在卷组VG之上。在逻辑卷LV之上可以建立文件系统（比如/home或者/usr等）。

查看信息命令

pvdisplay   #查看PV信息

[root@localhost ~]# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda3
  VG Name               VolGroup
  PV Size               18.51 GiB / not usable 3.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              4738
  Free PE               0
  Allocated PE          4738
  PV UUID               ARNJxr-gfcH-rW5H-X6I1-c2da-QhM1-BJ7ljo

vgdisplay   #查看VG信息

[root@localhost ~]# vgdisplay
  --- Volume group ---
  VG Name               VolGroup
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               18.51 GiB
  PE Size               4.00 MiB
  Total PE              4738
  Alloc PE / Size       4738 / 18.51 GiB
  Free  PE / Size       0 / 0   
  VG UUID               gFkWoE-8AVZ-kbd5-Clge-6Tq3-gcFh-4iVr1x

lvdisplay   #查看LV信息

[root@localhost ~]# lvdisplay
  --- Logical volume ---
  LV Path                /dev/VolGroup/LogVol01
  LV Name                LogVol01
  VG Name                VolGroup
  LV UUID                UeAMMJ-G6Ou-yMlJ-9Igz-pVBU-1HSy-jt6Trt
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2015-07-23 03:42:14 -0400
  LV Status              available
  # open                 1
  LV Size                4.05 GiB
  Current LE             1036
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0
   
  --- Logical volume ---
  LV Path                /dev/VolGroup/LogVol00
  LV Name                LogVol00
  VG Name                VolGroup
  LV UUID                OF62jU-eVGO-4Rtd-TycU-aoGC-0Rs0-nDRRhE
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2015-07-23 03:42:15 -0400
  LV Status              available
  # open                 1
  LV Size                14.46 GiB
  Current LE             3702
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:1

缩减和增加

减少swap分区空间前要取消挂载，使用 swapoff -a

[root@localhost ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          1877        140       1737          0          6         39
-/+ buffers/cache:         93       1783
Swap:         4143          0       4143
[root@localhost ~]# swapoff -a
[root@localhost ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          1877        136       1740          0          6         39
-/+ buffers/cache:         91       1786
Swap:            0          0          0

使用 lvreduce -L -xxx filename 或 lvreduce -L xxx filename 来减少swap分区空间，“-”代表减多少，不加“-”代表减剩多少。下图表示给swap分区留512M。

使用 mke2fs filename 格式化分区

使用 resize2fs filename 重写分区空间

[root@localhost ~]# lvreduce -L 512M /dev/VolGroup/LogVol01
  WARNING: Reducing active and open logical volume to 512.00 MiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce LogVol01? [y/n]: y
  Reducing logical volume LogVol01 to 512.00 MiB
  Logical volume LogVol01 successfully resized
[root@localhost ~]# mke2fs /dev/VolGroup/LogVol01
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
32768 inodes, 131072 blocks
6553 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=134217728
4 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
    32768, 98304

Writing inode tables: done                            
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 29 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@localhost ~]# resize2fs /dev/VolGroup/LogVol01
resize2fs 1.41.12 (17-May-2010)
The filesystem is already 131072 blocks long.  Nothing to do!

使用 lvextend -L +1G filename 为根分区增加空闲空间，用法同上。空闲空间可以使用vgdisplay查看，增加空间不需要格式化。

[root@localhost ~]# lvextend -L +3.54G /dev/VolGroup/LogVol00
  Rounding size to boundary between physical extents: 3.54 GiB
  Extending logical volume LogVol00 to 18.00 GiB
  Logical volume LogVol00 successfully resized
[root@localhost ~]# resize2fs /dev/VolGroup/LogVol00
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/VolGroup/LogVol00 is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 2
Performing an on-line resize of /dev/VolGroup/LogVol00 to 4719616 (4k) blocks.
The filesystem on /dev/VolGroup/LogVol00 is now 4719616 blocks long.

swap文件

新建2G的swap文件，挂载到swap,添加到开机启动项。

[root@localhost ~]# dd if=/dev/zero of=/www/swap bs=1024 count=2048000
2048000+0 records in
2048000+0 records out
2097152000 bytes (2.1 GB) copied, 12.0018 s, 175 MB/s
[root@localhost ~]# mkswap /www/swap 
mkswap: /www/swap: warning: don't erase bootbits sectors
        on whole disk. Use -f to force.
Setting up swapspace version 1, size = 2047996 KiB
no label, UUID=92ab4ed5-f301-4ba4-970f-9e5600610522
[root@localhost ~]# swapon /www/swap 
[root@localhost ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          1877       1796         80          0          7       1647
-/+ buffers/cache:        142       1735
Swap:         1999          0       1999
[root@localhost ~]# swapon -s
Filename                Type        Size    Used    Priority
/www/swap                               file        2047992    0    -1

修改启动项

编辑 /etc/fstab文件，去掉之前的swap分区挂载，在最末行增加swap文件的挂载

[root@localhost ~]# cat /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Thu Jul 23 03:45:08 2015
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/VolGroup-LogVol00 /                       ext4    defaults        1 1
UUID=4221a802-6ce2-4638-a3a5-7c17b961f291 /boot                   ext4    defaults        1 2
UUID=b720b68f-37b7-45ce-b4a2-40deeb9fa90f /www                    ext3    defaults        1 2
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
/www/swap               swap                    swap    defaults        0 0

重启后可以看到，根分区空间有增加， swap使用的是swap文件

[root@localhost ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-LogVol00
                       18G  716M   17G   5% /
tmpfs                 939M     0  939M   0% /dev/shm
/dev/sda1             485M   32M  429M   7% /boot
/dev/sda2              61G  2.2G   55G   4% /www
[root@localhost ~]# free -m
             total       used       free     shared    buffers     cached
Mem:          1877        135       1741          0          7         36
-/+ buffers/cache:         91       1786
Swap:         1999          0       1999
[root@localhost ~]# swapon -s
Filename                Type        Size    Used    Priority
/www/swap                               file        2047992    0    -1

注：之前有实验过直接删掉swap的LV，用文件代替，但是，删除swap的LV后,重启报错如图

按网上的解决办法，开机按“e”加“enforcing=0”神马的不管用。这个问题暂时木有解决，有解决过的老师，请告诉下学生。