8.5 mkfs：创建Linux文件系统
mkfs命令用于在指定的设备（或硬盘分区等）上创建格式化并创建文件系统，fdisk和parted等分区工具相当于建房的人，把房子（硬盘），分成几居室（分区），mkfs就相当于对不同的居室装修（创建文件系统）了，只有装修好的房子（有文件系统）才能入住，分区也是一样，只有格式化创建文件系统（存取数据的机制）后，才能用来存取数据。 mkfs [选项] [设备名] -t 指定要创建的文件系统类型 -c 创建文件系统时检查磁盘坏块 -v 显示详细信息 mkfs只是一个前端命令，它通过-t参数指定文件系统类型后会调用相应的命令mkfs.fstype。因此可以直接使用mkfs.ext4这个命令创建ext4文件系统。[root@cs6 ~]# ls /sbin/mkfs* /sbin/mkfs /sbin/mkfs.ext2 /sbin/mkfs.ext4 /sbin/mkfs.xfs /sbin/mkfs.cramfs /sbin/mkfs.ext3 /sbin/mkfs.ext4dev
通过mkfs 命令创建文件系统（-t参数）的例子
[root@cs6 ~]# mkfs -t ext4 -v /dev/sdb
mke2fs 1.41.12 (17-May-2010)
/dev/sdb is entire device, not just one partition!
Proceed anyway? (y,n) y
fs_types for mke2fs.conf resolution: 'ext4', 'default'
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
65536 inodes, 262144 blocks
13107 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=268435456
8 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 39 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
通过mkfs.ext4创建文件系统
[root@cs6 ~]# mkfs.ext4 /dev/sdb mke2fs 1.41.12 (17-May-2010) /dev/sdb is entire device, not just one partition! Proceed anyway? (y,n) y Filesystem label= OS type: Linux Block size=4096 (log=2) .... Creating journal (8192 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 25 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override.
8.6 dumpe2fs：导出ext2/ext3/ext4文件系统信息
dumpe2fs命令用于导出ext2/ext3/ext4文件系统内部的相关信息，例如：文件系统的组成包含超级快、块组、inode、block等信息。 dumpe2fs命令的参数选项及说明 -b 打印文件系统中预留的块信息 -h 仅显示超级块信息 -i 从指定的文件系统映像文件中读取文件的系统信息 -x 以16进制格式打印信息块成员查看系统的inode信息
[root@cs6 ~]# dumpe2fs /dev/sda1|egrep -i "inode size|inode count"
dumpe2fs 1.41.12 (17-May-2010)
Inode count: 128016 #<==单位；个。
Inode size: 128 #<== /boot 分区默认128字节。
[root@cs6 ~]# dumpe2fs /dev/mapper/vg_cs6-lv_root |egrep -i "inode size|inode count"
dumpe2fs 1.41.12 (17-May-2010)
Inode count: 1738080
Inode size: 256 #<==普通分区默认256字节。
[root@cs6 ~]# df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/mapper/vg_cs6-lv_root
1738080 23534 1714546 2% /
tmpfs 238145 1 238144 1% /dev/shm
/dev/sda1 128016 38 127978 1% /boot
[root@cs6 ~]# dumpe2fs /dev/sda1|egrep -i "block size|block count"
dumpe2fs 1.41.12 (17-May-2010)
Block count: 512000 #<==分区的block总量。
Reserved block count: 25600
Block size: 1024 #<==/boot分区默认1024字节即1K
[root@cs6 ~]# dumpe2fs /dev/mapper/vg_cs6-lv_root |egrep -i "block size|block count"
dumpe2fs 1.41.12 (17-May-2010)
Block count: 6948864
Reserved block count: 347443
Block size: 4096 #<==普通分区4K=4096字节。
8.7 resize2fs：调整ext2/ext3/ext4文件系统大小
resize2fs命令用于扩容或收缩未挂载的ext2/ext3/ext4文件系统。在Linux2.6或更高 版本的内核中，该命令还支持在线扩容已经挂载的文件系统，该命令常用来针对LVM扩容 后的分区使用。 -p 打印完成任务的进度条 -f 强制执行操作动态修改分区大小的例子
出现这种情况一般是当初对系统分区的时候没有规划好，现在想要重新调整分区的大小。假设是要对/dev/sdb上的分区进行操作，将/mnt/data1扩容。[root@cs6 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_cs6-lv_root
26G 834M 24G 4% /
tmpfs 931M 0 931M 0% /dev/shm
/dev/sda1 477M 28M 424M 7% /boot
/dev/sdb1 194M 1.8M 182M 1% /mnt/data1
/dev/sdb2 194M 1.8M 182M 1% /mnt/data2
[root@cs6 ~]# touch /mnt/data1/{1..5}.html
[root@cs6 ~]# touch /mnt/data2/{1..5}.html
提示：/dev/sdb是一块1GB的磁盘，现在分了两个主分区sdb1、sdb2，分别是200MB，剩余800MB未分区。现在需要把sdb2分区和sdb1分区合并，以实现对sdb1的扩容，注意，此种情况不要在生产场景操作，仅作为演示用，生产场景一般是事先规划好不会出现扩容需求，非I/O密集应用可以采用LVM实现规范动态扩容。 以下是扩容实战步骤。 1）记录分区的柱面起始信息：
[root@cs6 ~]# fdisk -l /dev/sdb Disk /dev/sdb: 1073 MB, 1073741824 bytes 255 heads, 63 sectors/track, 130 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x1bc7d413 Device Boot Start End Blocks Id System /dev/sdb1 1 26 208813+ 83 Linux /dev/sdb2 27 52 208845 83 Linux2）卸载分区：
[root@cs6 ~]# umount /mnt/data1
[root@cs6 ~]# umount /mnt/data2
[root@cs6 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_cs6-lv_root
26G 834M 24G 4% /
tmpfs 931M 0 931M 0% /dev/shm
/dev/sda1 477M 28M 424M 7% /boot
3）重新分区：
[root@cs6 ~]# fdisk /dev/sdb
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (command 'c') and change display units to
sectors (command 'u').
Command (m for help): d
Partition number (1-4): 1
Command (m for help): d
Selected partition 2
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-130, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-130, default 130): 52
Command (m for help): p
Disk /dev/sdb: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x1bc7d413
Device Boot Start End Blocks Id System
/dev/sdb1 1 52 417658+ 83 Linux
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[root@cs6 ~]# partprobe /dev/sdb
[root@cs6 ~]# mount /dev/sdb1 /mnt/data1
[root@cs6 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_cs6-lv_root
26G 834M 24G 4% /
tmpfs 931M 0 931M 0% /dev/shm
/dev/sda1 477M 28M 424M 7% /boot
/dev/sdb1 194M 1.8M 182M 1% /mnt/data1
[root@cs6 ~]# ls /mnt/data1
1.html 2.html 3.html 4.html 5.html lost+found
[root@cs6 ~]# resize2fs /dev/sdb1 #<==在线调整磁盘大小，
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/sdb1 is mounted on /mnt/data1; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 2
Performing an on-line resize of /dev/sdb1 to 417656 (1k) blocks.
The filesystem on /dev/sdb1 is now 417656 blocks long.
[root@cs6 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_cs6-lv_root
26G 834M 24G 4% /
tmpfs 931M 0 931M 0% /dev/shm
/dev/sda1 477M 28M 424M 7% /boot
/dev/sdb1 392M 2.3M 369M 1% /mnt/data1
[root@cs6 ~]# ls /mnt/data1
1.html 2.html 3.html 4.html 5.html lost+found
#<==但是数据还是只有sdb1里的了，sdb2的数据丢失了。此种方法不适合生产场景扩容，比较规范方法是通过LVM逻辑卷管理进行扩容，扩容后也需要resize2fs进行最终实现扩容。