Linux Disk Management
The quality of Linux disk management directly affects the performance of the entire system.
The three commonly used commands for Linux disk management are:df、duandfdisk。
- df(English full name: disk free): Lists the overall disk usage of the file system
- du(English full name: disk used): Checks disk space usage
- fdisk: Used for disk partitioning
df
The df command parameter function: Checks the disk space usage of the file system. You can use this command to obtain information such as how much space on the hard drive is occupied and how much space is currently remaining.
Syntax:
df [-ahikHTm] [目录或文件名]
Options and parameters:
-h: Displays output results in a human-readable format (e.g., using units such as KB, MB, GB).-T: Displays the file system type.-t <文件系统类型>: Only displays file systems of the specified type.-i: Displays inode usage.-H: This parameter is-ha variant of it, but uses 1000 bytes as the base unit instead of 1024 bytes. This means it displays disk usage in SI (International System of Units) units (such as MB, GB) rather than binary units (such as MiB, GiB).-k: This option displays disk space usage in KB as the unit.-a: This parameter displays all file systems, including virtual file systems, such asproc、sysfsetc. If this option is not used, by default,dfthe command will not display virtual file systems.
Example 1
List all file systems on the system!
[root@www ~]# df Filesystem 1K-blocks Used Available Use% Mounted on /dev/hdc2 9920624 3823112 5585444 41% / /dev/hdc3 4956316 141376 4559108 4% /home /dev/hdc1 101086 11126 84741 12% /boot tmpfs 371332 0 371332 0% /dev/shm
In Linux, if df is used without any options, by default it will list all file systems in the system (excluding special in-memory file systems and swap) with a capacity of 1 Kbytes!
Example 2
Display the capacity results in a readable capacity format
[root@www ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/hdc2 9.5G 3.7G 5.4G 41% / /dev/hdc3 4.8G 139M 4.4G 4% /home /dev/hdc1 99M 11M 83M 12% /boot tmpfs 363M 0 363M 0% /dev/shm
Example 3
List all special file formats and names in the system
[root@www ~]# df -aT Filesystem Type 1K-blocks Used Available Use% Mounted on /dev/hdc2 ext3 9920624 3823112 5585444 41% / proc proc 0 0 0 - /proc sysfs sysfs 0 0 0 - /sys devpts devpts 0 0 0 - /dev/pts /dev/hdc3 ext3 4956316 141376 4559108 4% /home /dev/hdc1 ext3 101086 11126 84741 12% /boot tmpfs tmpfs 371332 0 371332 0% /dev/shm none binfmt_misc 0 0 0 - /proc/sys/fs/binfmt_misc sunrpc rpc_pipefs 0 0 0 - /var/lib/nfs/rpc_pipefs
Example 4
Display the available disk capacity under /etc in a readable capacity format
[root@www ~]# df -h /etc Filesystem Size Used Avail Use% Mounted on /dev/hdc2 9.5G 3.7G 5.4G 41% /
du
The Linux du command is also used to view used space, but unlike the df command, the Linux du command checks the disk space used by files and directories. It still has some differences from the df command. Here we introduce the Linux du command.
Syntax:
du [-ahskm] 文件或目录名称
Options and parameters:
- -a: Lists the capacity of all files and directories, because by default only the file amounts under directories are counted.
- -h: Displays in a more human-readable capacity format (G/M);
- -s: Only displays the total size of the specified directory or file, without showing the sizes of its subdirectories.
- -S: Includes the total of subdirectories, which is somewhat different from -s.
- -k: Lists capacity in KBytes;
- -m: Lists capacity in MBytes;
Example 1
Only list the capacity of all folders in the current directory (including hidden folders):
[root@www ~]# du 8 ./test4 <==每个目录都会列出来 8 ./test2 ....中间省略.... 12 ./.gconfd <==包括隐藏文件的目录 220 . <==这个目录(.)所占用的总量
When du is entered directly without any options, du will analyze the hard disk space occupied by subdirectories in the current directory.
Example 2
Also list the capacity of files
[root@www ~]# du -a 12 ./install.log.syslog <==有文件的列表了 8 ./.bash_logout 8 ./test4 8 ./test2 ....中间省略.... 12 ./.gconfd 220 .
Example 3
Check the capacity occupied by each directory under the root directory
[root@www ~]# du -sm /* 7 /bin 6 /boot .....中间省略.... 0 /proc .....中间省略.... 1 /tmp 3859 /usr <==系统初期最大就是他了啦！ 77 /var
The wildcard * is used to represent each directory.
Unlike df, the du command actually goes directly into the file system to search for all file data.
fdisk
fdisk is a disk partition table operation tool for Linux.
Syntax:
fdisk [-l] 装置名称
Options and parameters:
- -l: Outputs all partition content of the device that follows. If only fdisk -l is used, the system will list all partitions of devices that can be found in the entire system.
Example 1
List all partition information
[root@AY120919111755c246621 tmp]# fdisk -l
Disk /dev/xvda: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 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: 0x00000000
Device Boot Start End Blocks Id System
/dev/xvda1 * 1 2550 20480000 83 Linux
/dev/xvda2 2550 2611 490496 82 Linux swap / Solaris
Disk /dev/xvdb: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 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: 0x56f40944
Device Boot Start End Blocks Id System
/dev/xvdb2 1 2610 20964793+ 83 Linux
Example 2
Find the disk where the root directory is located in your system, and view the relevant information on that hard disk
[root@www ~]# df / <==注意：重点在找出磁盘文件名而已 Filesystem 1K-blocks Used Available Use% Mounted on /dev/hdc2 9920624 3823168 5585388 41% / [root@www ~]# fdisk /dev/hdc <==仔细看，不要加上数字喔！ The number of cylinders for this disk is set to 5005. There is nothing wrong with that, but this is larger than 1024, and could in certain setups cause problems with: 1) software that runs at boot time (e.g., old versions of LILO) 2) booting and partitioning software from other OSs (e.g., DOS FDISK, OS/2 FDISK) Command (m for help): <==等待你的输入！
After entering m, you will see the introduction to these commands below
Command (m for help): m <== 输入 m 后，就会看到底下这些命令介绍 Command action a toggle a bootable flag b edit bsd disklabel c toggle the dos compatibility flag d delete a partition <==删除一个partition l list known partition types m print this menu n add a new partition <==新增一个partition o create a new empty DOS partition table p print the partition table <==在屏幕上显示分割表 q quit without saving changes <==不储存离开fdisk程序 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 <==将刚刚的动作写入分割表 x extra functionality (experts only)
When leaving fdisk, pressq, then all actions will not take effect! Conversely, pressingwmeans the actions take effect.
Command (m for help): p <== 这里可以输出目前磁盘的状态 Disk /dev/hdc: 41.1 GB, 41174138880 bytes <==这个磁盘的文件名与容量 255 heads, 63 sectors/track, 5005 cylinders <==磁头、扇区与磁柱大小 Units = cylinders of 16065 * 512 = 8225280 bytes <==每个磁柱的大小 Device Boot Start End Blocks Id System /dev/hdc1 * 1 13 104391 83 Linux /dev/hdc2 14 1288 10241437+ 83 Linux /dev/hdc3 1289 1925 5116702+ 83 Linux /dev/hdc4 1926 5005 24740100 5 Extended /dev/hdc5 1926 2052 1020096 82 Linux swap / Solaris # 装置文件名 启动区否 开始磁柱 结束磁柱 1K大小容量 磁盘分区槽内的系统 Command (m for help): q
Want to leave without saving? Just press q! Don't press w carelessly!
Usepto list the partition table information of the current disk. The upper part of this information displays the overall status of the disk.
Disk Formatting
After disk partitioning is complete, the natural next step is to format the file system. The formatting command is very simple; use themkfs(make filesystem) command.
Syntax:
mkfs [-t 文件系统格式] 装置文件名
Options and parameters:
- -t: Can take a file system format, such as ext3, ext2, vfat, etc. (It only takes effect if the system supports it)
Example 1
View the file formats supported by mkfs
[root@www ~]# mkfs[tab][tab] mkfs mkfs.cramfs mkfs.ext2 mkfs.ext3 mkfs.msdos mkfs.vfat
Press [tab] twice, and you will find that the file formats supported by mkfs are as shown above.
Example 2
Format the partition /dev/hdc6 (you can specify your own partition) as an ext3 file system:
[root@www ~]# mkfs -t ext3 /dev/hdc6
mke2fs 1.39 (29-May-2006)
Filesystem label= <==这里指的是分割槽的名称(label)
OS type: Linux
Block size=4096 (log=2) <==block 的大小配置为 4K
Fragment size=4096 (log=2)
251392 inodes, 502023 blocks <==由此配置决定的inode/block数量
25101 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=515899392
16 block groups
32768 blocks per group, 32768 fragments per group
15712 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Writing inode tables: done
Creating journal (8192 blocks): done <==有日志记录
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 34 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
# 这样就创建起来我们所需要的 Ext3 文件系统了！简单明了！
Disk Check
fsck (file system check) is used to check and maintain inconsistent file systems.
If the system loses power or the disk has problems, the fsck command can be used to check the file system.
Syntax:
fsck [-t 文件系统] [-ACay] 装置名称
Options and parameters:
- -t: Specifies the type of the file system. If it is already defined in /etc/fstab or is already supported by the kernel itself, this parameter does not need to be added.
- -s: Executes fsck commands one by one in sequence to check.
- -A: Checks all partitions listed in /etc/fstab.
- -C: Displays the complete check progress.
- -d: Prints the debug results of e2fsck.
- -p: When combined with the -A condition, multiple fsck checks are executed together at the same time.
- -R: When combined with the -A condition, omits / and does not check it.
- -V: Verbose display mode.
- -a: Automatically repairs if errors are found during the check.
- -r: If errors are found during the check, the user is asked whether to repair them.
- -y: The option specifies that yes is automatically input for checking each file. When you are not sure which files are abnormal, you can execute # fsck -y to check and repair everything.
Example 1
View how many file system fsck commands are supported by the system:
[root@www ~]# fsck[tab][tab] fsck fsck.cramfs fsck.ext2 fsck.ext3 fsck.msdos fsck.vfat
Example 2
Forcefully check the /dev/hdc6 partition:
[root@www ~]# fsck -C -f -t ext3 /dev/hdc6 fsck 1.39 (29-May-2006) e2fsck 1.39 (29-May-2006) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information vbird_logical: 11/251968 files (9.1% non-contiguous), 36926/1004046 blocks
If the -f option is not added, since this file system has never had problems, the check process will be very fast! Only if -f is added for a forced check will the process be displayed item by item.
Disk Mounting and Unmounting
Linux disk mounting uses themountcommand, and unmounting uses theumountcommand.
Disk mounting syntax:
mount [-t 文件系统] [-L Label名] [-o 额外选项] [-n] 装置文件名 挂载点
Example 1
Use the default method to mount the just-created /dev/hdc6 to /mnt/hdc6!
[root@www ~]# mkdir /mnt/hdc6 [root@www ~]# mount /dev/hdc6 /mnt/hdc6 [root@www ~]# df Filesystem 1K-blocks Used Available Use% Mounted on .....中间省略..... /dev/hdc6 1976312 42072 1833836 3% /mnt/hdc6
Disk unmount commandumountSyntax:
umount [-fn] 装置文件名或挂载点
Options and parameters:
- -f: Force unmount! Can be used in situations such as when a network file system (NFS) cannot be read;
- -n: Unmount without updating /etc/mtab.
Unmount /dev/hdc6
[root@www ~]# umount /dev/hdc6Other Extensions