概念
我理解挂载就是将磁盘和目录关联起来，当然也可以目录和目录关联
使用
通过fdisk可以查看磁盘分区情况
fsdisk -l
查询结果
[root@lazy ~]# fdisk -l Disk /dev/sda: 500.1 GB, 500107862016 bytes, 976773168 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 label type: dos Disk identifier: 0xdced7faf Device Boot Start End Blocks Id System /dev/sda1 * 2048 100677631 50337792 7 HPFS/NTFS/exFAT /dev/sda2 100677632 101701631 512000 83 Linux /dev/sda3 101701632 654843903 276571136 8e Linux LVM Disk /dev/mapper/centos-root: 53.7 GB, 53687091200 bytes, 104857600 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 /dev/mapper/centos-swap: 4026 MB, 4026531840 bytes, 7864320 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 /dev/mapper/centos-home: 214.7 GB, 214748364800 bytes, 419430400 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 /dev/mapper/centos-var: 10.7 GB, 10737418240 bytes, 20971520 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
可以看出我的机器上有一块硬盘/dev/sda ，500G大小，被分成了三个区，其中sda3被创建为LVM 物理卷，有4个逻辑卷。三一个区大小总和不到500G,说明还有可被分配的空间，使用fdisk进行分区
[root@lazy home]# fdisk /dev/sda
Welcome to fdisk (util-linux 2.23.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.
Command (m for help): n
Partition type:
p primary (3 primary, 0 extended, 1 free)
e extended
Select (default e): p
Selected partition 4
First sector (654843904-976773167, default 654843904):
Using default value 654843904
Last sector, +sectors or +size{K,M,G} (654843904-976773167, default 976773167):
Using default value 976773167
Partition 4 of type Linux and of size 153.5 GiB is set
Command (m for help): p
Disk /dev/sda: 500.1 GB, 500107862016 bytes, 976773168 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 label type: dos
Disk identifier: 0xdced7faf
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 100677631 50337792 7 HPFS/NTFS/exFAT
/dev/sda2 100677632 101701631 512000 83 Linux
/dev/sda3 101701632 654843903 276571136 8e Linux LVM
/dev/sda4 654843904 976773167 160964632 83 Linux
命令说明：
n # 新建分区
-e # 创建扩展分区)
-p # 创建主分区)
-t # 改变分区类型)
p # 查看分区
w # 将信息写入磁盘
使用df 命令查看磁盘挂载情况
[root@lazy home]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/centos-root 50G 1.7G 49G 4% / devtmpfs 847M 0 847M 0% /dev tmpfs 859M 0 859M 0% /dev/shm tmpfs 859M 33M 826M 4% /run tmpfs 859M 0 859M 0% /sys/fs/cgroup /dev/mapper/centos-home 200G 16G 184G 8% /home /dev/mapper/centos-var 10G 8.1G 2.0G 81% /var /dev/sda2 497M 130M 367M 27% /boot tmpfs 172M 0 172M 0% /run/user/0
创建目录/mnt/haha，将刚刚创建的分区sda4 挂载到该目录
[root@lazy /]# mkdir /mnt/haha
[root@lazy /]# mount /dev/sda4 /mnt/haha
发现报错mount: special device /dev/sda4 does not exist，找不到分区，查看/pro/partitions
[root@lazy /]# cat /proc/partitions major minor #blocks name 11 0 1048575 sr0 8 0 488386584 sda 8 1 50337792 sda1 8 2 512000 sda2 8 3 276571136 sda3 253 0 52428800 dm-0 253 1 3932160 dm-1 253 2 209715200 dm-2 253 3 10485760 dm-3
确实没有分区sda4,这时需要让内核重读磁盘分区表，可以通过partx工具让内核重读磁盘分区表
partx -d /dev/sda //所有信息清零 partx -a /dev/sda //添加分区信息 partx -s /dev/sda //显示分区信息
再进行挂载，报错
mount: unknown filesystem type '(null)'
格式化分区
mkfs -t ext2 /dev/sda4
挂载不再报错，df -h 查看
[root@lazy haha]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/centos-root 50G 1.7G 49G 4% / devtmpfs 847M 0 847M 0% /dev tmpfs 859M 0 859M 0% /dev/shm tmpfs 859M 33M 826M 4% /run tmpfs 859M 0 859M 0% /sys/fs/cgroup /dev/mapper/centos-home 200G 16G 184G 8% /home /dev/mapper/centos-var 10G 8.1G 2.0G 81% /var /dev/sda2 497M 130M 367M 27% /boot tmpfs 172M 0 172M 0% /run/user/0 /dev/sda4 152G 60M 144G 1% /mnt/haha [root@lazy haha]#
可以利用umount取消挂载
[root@lazy haha]# umount /mnt/haha [root@lazy haha]# df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/centos-root 50G 1.7G 49G 4% / devtmpfs 847M 0 847M 0% /dev tmpfs 859M 0 859M 0% /dev/shm tmpfs 859M 33M 826M 4% /run tmpfs 859M 0 859M 0% /sys/fs/cgroup /dev/mapper/centos-home 200G 16G 184G 8% /home /dev/mapper/centos-var 10G 8.1G 2.0G 81% /var /dev/sda2 497M 130M 367M 27% /boot tmpfs 172M 0 172M 0% /run/user/0 [root@lazy haha]#
/etc/fstab和/etc/mtab
/etc/fstab 记录了计算机上硬盘分区的相关信息，启动 Linux 的时候，检查分区的 fsck 命令，和挂载分区的 mount 命令，都需要 fstab 中的信息，来正确的检查和挂载硬盘。 所以可以在这个文件中加入挂载盘的信息，实现启动时挂载；
[root@lazy haha]# cat /etc/fstab # # /etc/fstab # Created by anaconda on Sun Mar 6 22:36:43 2016 # # 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/centos-root / xfs defaults 0 0 UUID=846e966f-11ed-4b3f-b7d4-ddfff975cb6a /boot xfs defaults 0 0 /dev/mapper/centos-home /home xfs defaults 0 0 /dev/mapper/centos-var /var xfs defaults 0 0 /dev/mapper/centos-swap swap swap defaults 0 0 [root@lazy haha]#
用第一行来说明各列代表的含义，
- /dev/mapper/centeros-home 可以是设备名称、LABEL UUID 伪文件系统名称
- / 挂载点，即指定的文件目录
- xfs 文件系统类型
- defaults 挂载选项
- 0 存储频率 0 不做备份，1 每天转储，2 每隔一天转储
- 0 自检次序 0 不自检，1 首先自检，一般只有rootfs 才用到
/etc/mtab 记载的是现在系统已经装载的文件系统，包括操作系统建立的虚拟文件等；而/etc/fstab是系统准备装载的。 每当 mount 挂载分区、umount 卸载分区，都会动态更新 mtab，mtab 总是保持着当前系统中已挂载的分区信息，fdisk、df 这类程序，必须要读取 mtab 文件，才能获得当前系统中的分区挂载情况。当然我们自己还可以通过读取/proc/mount也可以来获取当前挂载信息