磁盘分区原理与规则
磁盘分区类型：主分区，扩展分区，逻辑分区。 分区规则： 1. 主分区+扩展分区的数量不能超过4个，且扩展分区只能有1个。逻辑分区要在扩展分区之上进行划分，逻辑分区没有数量限制，可以任意个。 2. 扩展分区是不能直接用的，他是以逻辑分区的方式来使用的，所以说扩展分区可分成若干逻辑分区。他们的关系是包含的关系，所有的逻辑分区都是扩展分区的一部分。 3. 硬盘的容量=主分区的容量+扩展分区的容量；扩展分区的容量=各个逻辑分区的容量之和
主分区就是普通磁盘分盘，但是由于磁盘设备由大量的扇区组成，一个扇区的容量为512字节。
磁盘的第一个扇区最为重要，记录了主引导记录与分区表信息。
就第一个扇区而言，主引导信息记录需要占用466个字节，分区表64个字节，结束符占用2个字节；
其中分区表中每记录一个分区信息就需要16个字节，所以最多只有4个分区信息可以记录在第一个扇区中，所以主分区+扩展分区的数量不能超过4个。
但是为了创建更多的分区，就使用扩展分区做份下若干个分区的指针，划分若干个逻辑分区，来满足分区数大于4个的需求。 扩展分区不需要挂载，但是可以格式化。
- 查看
# fdisk -l Disk /dev/vda: 85.9 GB, 85899345920 bytes, 167772160 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: 0x000b2d99 Device Boot Start End Blocks Id System /dev/vda1 * 2048 167766794 83882373+ 83 Linux Disk /dev/vdb: 128.8 GB, 128849018880 bytes, 251658240 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
挂载成功的磁盘会有此栏:
Disk label type: dos
Disk identifier: 0x000b2d99
Device Boot Start End Blocks Id System
/dev/vda1 * 2048 167766794 83882373+ 83 Linux
上面的信息显示/dev/vda已挂载，/dev/vdb未挂载.
创建分区
# fdisk /dev/vdb 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. Device does not contain a recognized partition table Building a new DOS disklabel with disk identifier 0x9b667550. Command (m for help): m Command action a toggle a bootable flag b edit bsd disklabel c toggle the dos compatibility flag d delete a partition 删除分区 g create a new empty GPT partition table G create an IRIX (SGI) partition table l list known partition types m print this menu n add a new partition 创建一个新分区 o create a new empty DOS partition table p print the partition table q quit without saving changes 退出时，保存变更 s create a new empty Sun disklabel t change a partition's system id u change display/entry units v verify the partition table w write table to disk and exit 写入分区表 x extra functionality (experts only) Command (m for help): n Partition type: #分区类型 p primary (0 primary, 0 extended, 4 free) 主分区 e extended 扩展分区 Select (default p): Using default response p Partition number (1-4, default 1): 分区标识号 First sector (2048-251658239, default 2048): Using default value 2048 分区起点 Last sector, +sectors or +size{K,M,G} (2048-251658239, default 251658239): Using default value 251658239 分区终点 Partition 1 of type Linux and of size 120 GiB is set Command (m for help): wq The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.再次查看
# fdisk -l Disk /dev/vda: 85.9 GB, 85899345920 bytes, 167772160 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: 0x000b2d99 Device Boot Start End Blocks Id System /dev/vda1 * 2048 167766794 83882373+ 83 Linux Disk /dev/vdb: 128.8 GB, 128849018880 bytes, 251658240 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: 0x9b667550 Device Boot Start End Blocks Id System /dev/vdb1 2048 251658239 125828096 83 Linux格式化分区
# mkfs -t ext4 /dev/vdb1 mke2fs 1.42.9 (28-Dec-2013) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=0 blocks, Stripe width=0 blocks 7864320 inodes, 31457024 blocks 1572851 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=2178940928 960 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624, 11239424, 20480000, 23887872 Allocating group tables: done Writing inode tables: done Creating journal (32768 blocks): done Writing superblocks and filesystem accounting information: done挂载分区
mount /dev/vdb1 /data卸载分区
umount /dev/vdb1永久挂载
vi /etc/fstab # `/dev/sdb1` 分区名 `/data` 挂载路径 `ext4` 格式,其他默认） /dev/sdb1 /data/primary ext4 defaults 0 0查看分区信息
# df -h Filesystem Size Used Avail Use% Mounted on devtmpfs 7.8G 0 7.8G 0% /dev tmpfs 7.8G 0 7.8G 0% /dev/shm tmpfs 7.8G 452K 7.8G 1% /run tmpfs 7.8G 0 7.8G 0% /sys/fs/cgroup /dev/vda1 79G 3.0G 73G 4% / tmpfs 1.6G 0 1.6G 0% /run/user/0 /dev/vdb1 118G 61M 112G 1% /data