首先这里说的调整指的是增加，目前还没有遇到需要单独减小硬盘的情况,分区用默认的ext2/3/4

一、关机, xencenter中调整硬盘大小

二、开机，fadisk相关操作
df -l -BG 然后 fdisk -l 查看映射、硬盘大小是否已经调整成功，vps中默认的一般是 /dev/xvda，如下所示

Disk /dev/xvda: 32.2 GB, 32212254720 bytes
255 heads, 63 sectors/track, 3916 cylinders, total 62914560 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000c9e45

    Device Boot      Start         End      Blocks   Id  System
/dev/xvda1            2048    15988735     7993344   83  Linux
/dev/xvda2        15990782    16775167      392193    5  Extended
/dev/xvda5        15990784    16775167      392192   82  Linux swap / Solaris

硬盘大小已成功调整为32.2GB，那么接下来就是重建分区表来使用这32.2GB
执行 fdisk /dev/xvda 按提示操作，p 显示分区表，d 删除分区, n 新建分区，w保存分区表
把上面3个分区全删除后新建为一整个分区，执行完成后应如下所示

Disk /dev/xvda: 32.2 GB, 32212254720 bytes
64 heads, 51 sectors/track, 19275 cylinders, total 62914560 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0008292e

    Device Boot      Start         End      Blocks   Id  System
/dev/xvda1            2048    62914559    31456256   83  Linux

重启生效。
三、resize2fs 调整映射大小
执行 resize2fs -p /dev/xvda1 和 df -l -BG 查看映射是否调整成功
—EOF–

番外篇：xencenter中自带模版建vps硬盘最小8G，而实际上linux vps硬盘1G即可，登录xenserver命令行可调整

#查找模版uuid，比如debian 7 wheezy 64-bit
[root@xen ~]# xe template-list|grep -b1 64-bit|grep -b1 Wheezy
819-2091-uuid ( RO)                : c6f1c77e-09eb-b3c4-bf5c-3ac6113c085a
...

#读取配置
[root@xen ~]# xe template-param-get uuid=c6f1c77e-09eb-b3c4-bf5c-3ac6113c085a param-name=other-config
disks: <provision><disk device="0" size="8589934592" sr="" bootable="false" type="system"/></provision>; mac_seed: ...

#修改配置：8589934592=8G，2147483648=2G，1073741824=1G
[root@xen ~]# xe template-param-set uuid=c6f1c77e-09eb-b3c4-bf5c-3ac6113c085a other-config:disks='<provision><disk device="0" size="2147483648" sr="" bootable="false" type="system"/></provision>'

#检查配置
[root@xen ~]# xe template-param-get uuid=c6f1c77e-09eb-b3c4-bf5c-3ac6113c085a param-name=other-config
disks: <provision><disk device="0" size="2147483648" sr="" bootable="false" type="system"/></provision>; mac_seed: ...

参考资料：
https://www.schirmacher.de/display/INFO/How+to+increase+XenServer+virtual+machine+root+or+swap+partition
https://maanasroyy.wordpress.com/2012/06/03/resize-a-linux-vm-lvm-disk-in-xenserver/