Ubuntu挂载硬盘

通常，磁盘添加完成后，需要重启一下计算机，内核会自动检测到这个新的设备。
但是，在生产环境中我们需要不重启而让内核检测到SCSI磁盘。
``` sh
root@ubuntu:/# ls /sys/class/scsi_host/  -- 查看主机总线号
host0 host1 host2
root@ubuntu:/# echo "- - -" > /sys/class/scsi_host/host0/scan  -- 重新扫描SCSI总线来添加设备
root@ubuntu:/# echo "- - -" > /sys/class/scsi_host/host1/scan
root@ubuntu:/# echo "- - -" > /sys/class/scsi_host/host2/scan
```

``` sh
root@ubuntu:/data# fdisk -l    -- 查看硬盘分区信息

Device     Boot   Start      End  Sectors  Size Id Type
/dev/vda1  *       2048   999423   997376  487M 83 Linux
/dev/vda2       1001470 41940991 40939522 19.5G  5 Extended
/dev/vda5       1001472 41940991 40939520 19.5G 8e Linux LVM

Disk /dev/vdb: 500 GiB, 536870912000 bytes, 1048576000 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

root@ubuntu:/data# fdisk /dev/vdb     -- 使用fdisk工具对sdb进行分区

Welcome to fdisk (util-linux 2.27.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0xed191ac7.

Command (m for help): m    -- 列出fdisk的帮助信息

Help:

DOS (MBR)
   a   toggle a bootable flag
   b   edit nested BSD disklabel
   c   toggle the dos compatibility flag

Generic
   d   delete a partition
   F   list free unpartitioned space
   l   list known partition types
   n   add a new partition
   p   print the partition table
   t   change a partition type
   v   verify the partition table
   i   print information about a partition

Misc
   m   print this menu
   u   change display/entry units
   x   extra functionality (experts only)

Script
   I   load disk layout from sfdisk script file
   O   dump disk layout to sfdisk script file

Save & Exit
   w   write table to disk and exit
   q   quit without saving changes

Create a new label
   g   create a new empty GPT partition table
   G   create a new empty SGI (IRIX) partition table
   o   create a new empty DOS partition table
   s   create a new empty Sun partition table

Command (m for help): p

Disk /dev/vdb: 500 GiB, 536870912000 bytes, 1048576000 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
Disklabel type: dos
Disk identifier: 0xed191ac7

Command (m for help): n                -- 增加一个分区
Partition type                         -- 选择是建立主分区还是扩展分区
   p   primary (0 primary, 0 extended, 4 free)
   e   extended (container for logical partitions)
Select (default p): p                  -- 建立主分区
Partition number (1-4, default 1):     -- 输入分区号
First sector (2048-1048575999, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-1048575999, default 1048575999):

Created a new partition 1 of type 'Linux' and of size 500 GiB.

Command (m for help): p
Disk /dev/vdb: 500 GiB, 536870912000 bytes, 1048576000 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
Disklabel type: dos
Disk identifier: 0xed191ac7

Device     Boot Start        End    Sectors  Size Id Type
/dev/vdb1        2048 1048575999 1048573952  500G 83 Linux

Command (m for help): w                -- 保存
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

root@ubuntu:/data# mkfs.ext4 /dev/vdb1        -- 格式化新建的分区
mke2fs 1.42.13 (17-May-2015)
Creating filesystem with 131071744 4k blocks and 32768000 inodes
Filesystem UUID: 2949eb1a-4ea4-4238-b27a-4d3142fc472c
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
        4096000, 7962624, 11239424, 20480000, 23887872, 71663616, 78675968,
        102400000

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information:
done

root@ubuntu:/data# mkdir /data --建立一个新的挂载目录
root@ubuntu:/data# mount /dev/vdb1 /data
root@ubuntu:/data# df -h
Filesystem                   Size  Used Avail Use% Mounted on
udev                         3.9G     0  3.9G   0% /dev
tmpfs                        799M  8.8M  790M   2% /run
/dev/mapper/ubuntu--vg-root   20G  1.8G   17G  10% /
tmpfs                        3.9G     0  3.9G   0% /dev/shm
tmpfs                        5.0M     0  5.0M   0% /run/lock
tmpfs                        3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/vda1                    472M   57M  392M  13% /boot
tmpfs                        100K     0  100K   0% /run/lxcfs/controllers
tmpfs                        799M     0  799M   0% /run/user/1000
/dev/vdb1                    493G   70M  467G   1% /data        -- 挂载成功

```

```
到此为止，我们的新硬盘已经加载成功了，但是这里有一个问题，一旦我们重新启动系统，还需要用mount命令重新挂接才能访问新硬盘，
如果需要在系统启动时自动挂载，那么需要用vi配置/etc/fstab文件,
将/dev/vdb1  /data   ext4  defaults    1 1 添加到/etc/fstab的最后，然后重新启动系统即可。

第一列为设备号或该设备的卷标
第二列为挂载点
第三列为文件系统
第四列为文件系统参数
第五列为是否可以用demp命令备份。0：不备份，1：备份，2：备份，但比1重要性小。设置了该参数后，Linux中使用dump命令备份系统的时候就可以备份相应设置的挂载点了。
第六列为是否在系统启动的时候，用fsck检验分区。因为有些挂载点是不需要检验的，比如：虚拟内存swap、/proc等。0：不检验，1：要检验，2要检验，但比1晚检验，一般根目录设置为1，其他设置为2就可以了。

解除挂载
umount /dev/sdb1
查看分区是ext3还是ext4系统

df -hT
```