我正在尝试安装设备但没有成功。奇怪的是mount命令成功，返回退出码0，但是设备并没有挂载。关于为什么会发生这种情况或如何进行调查的任何想法？请看下面的例子：
[root@mymachine ~]# blkid -o list
device fs_type label mount point UUID
-----------------------------------------------------------------------------------------
/dev/xvda1 xfs / 29342a0b-e20f-4676-9ecf-dfdf02ef6683
/dev/xvdy ext4 /vols/data 72c23c30-2704-42ec-9518-533c182e2b22
/dev/xvdb swap <swap> 990ff722-158c-4ad5-963a-0bc9e1e2b17a
/dev/xvdx ext4 (not mounted) 956b5553-d8b4-4ffe-830c-253e1cb10a2f
[root@mymachine ~]# grep /dev/xvdx /etc/fstab
/dev/xvdx /vols/data5 ext4 defaults 0 0
[root@mymachine ~]# mount -a; echo $?
0
[root@mymachine ~]# blkid -o list
device fs_type label mount point UUID
-----------------------------------------------------------------------------------------
/dev/xvda1 xfs / 29342a0b-e20f-4676-9ecf-dfdf02ef6683
/dev/xvdy ext4 /vols/data 72c23c30-2704-42ec-9518-533c182e2b22
/dev/xvdb swap <swap> 990ff722-158c-4ad5-963a-0bc9e1e2b17a
/dev/xvdx ext4 (not mounted) 956b5553-d8b4-4ffe-830c-253e1cb10a2f
[root@mymachine ~]# mount …