Live Resize of Logical Volume in RHEL/CentOS

以下技术应用于最优质的水果的鲜果篮

The default installation of RHEL 6 and CentOS 6 will create separate LVM volumes for /home. This means much of your disk is allocated to /home when it could be used for something else. Keeping /home on a separate partition is a good idea for multi-user systems, but for machines that act as a service box, it may be wasted disk space. For example, here’s a system that has 50G partitioned for /home when it’s really not needed.

1$ df -h

2Filesystem                  Size  Used Avail Use% Mounted on

3/dev/mapper/vg_repo-lv_root 148G  113G   29G  80% /

4tmpfs                       499M     0  499M   0% /dev/shm

5/dev/sda1                   485M  156M  304M  34% /boot

6/dev/mapper/vg_repo-lv_home 47G  181M   45G   1%  /home

To remove the logical volume that stores /home and add the free space to the root partition, follow these steps:

Note: Make sure you’re logged into the system at the console as a user whose homedir isn’t in /home. Logging in as root usually works.

1cd /

2cp -Ra /home /home.bak  # Make a backup of home

3umount /home

4lvm lvremove /dev/vg_<hostname>/lv_home  # Remove the logical volume for home

5lvm lvresize -l+100%FREE /dev/vg_<hostname>/lv_root  # Resize the root logical volume so it uses 100% of the now free space

6resize2fs /dev/vg_<hostname>/lv_root  # Resize the filesystem to use the whole logical volume

7mv /home.bak /home  # Restore the backup.

More Notes:

• This can be done on a live system as long as /home is not in use when you try to unmount it.
• You can also follow these steps to resize another logical volume if it has another name and isn’t in use.
• This may work with some adjustments on a RHEL/CentOS 5 system, I haven’t tried it though.

请注意，以上操作以后还需要这样的重要一步，否则系统如果重启将无法启动：

编辑/etc/fstab，删除掉/dev/mapper/vg_repo-lv_home对应的那一行。

如果遗漏了这一步，服务器重启后，CentOS将无法启动，会进入到 (Repair Filesystem) 提示符。CentOS会报告挂载 /home 分区错误。
这时在 (Repair Filesystem) 中使用任何lvm管理命令都是无效的。如输入 lvdisplay lvs pvs vgs 等命令，都会显示同一个错误：File-based locking initialisation failed。

为了解决这个问题，先要将原来挂载/home的分区的部分取消。可是在 (Repair Filesystem) 提示符下，对硬盘的管理是只读的，修改 /etc/fstab 将不能保存。
要解决这个问题，需要重新挂载文件系统为可写。在 (Repair Filesystem) 中输入 root 密码之后，输入如下命令：mount -w -o remount /
然后再次编辑 /etc/fstab ，删除掉/dev/mapper/vg_repo-lv_home对应的那一行，重启即可正常进入系统。