Linux disk management
The quality of Linux disk management is directly related to the performance of the entire system.
The three commonly used commands for Linux disk management are df, du and fdisk.
df: List the overall disk usage of the file system
du: Check the disk space usage
fdisk: used for disk partitions
df
df command parameter function: Check the disk space usage of the file system. You can use this command to obtain information such as how much space is occupied on the hard disk and how much space is currently left.
Syntax:
df [-ahikHTm] [目录或文件名]
Options and parameters:
-a: List all file systems, including system-specific /proc and other file systems ;
-k : Display each file system in KBytes capacity;
#-m : Display each file system in MBytes capacity;
-h: Display in GBytes, MBytes, KBytes and other formats that are easier for people to read;
-H: Replace with M=1000K M=1024K carry mode;
-T: Display the file system type, together with the filesystem name of the partition (such as ext3) is also listed;
-
-i: Do not use the hard disk capacity, but display the number of inodes
Example 1
List all file systems in 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
Under Linux, if df does not add any options, all the files in the system will be (Excluding the file system and swap in special memory) are listed with a capacity of 1 Kbytes!
Example 2
Display the capacity results in an easy-to-read 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
Display all special file formats and names in the system List them all
[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 an easy-to-read 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 #inux du command also checks the space used, but unlike the df command, the Linux du command checks the space used by files and directory disks, which is somewhat different from the df command. Here is the Linux du command. Syntax:du [-ahskm] 文件或目录名称Options and parameters:
- -a: List all files and directory capacities, because by default only the contents under the directory are counted Just the amount of files.
- -h: Display in capacity format (G/M) that is easier for people to read;
- -s: List the total amount only , without listing the capacity occupied by each individual directory;
- -S: excluding the total number of subdirectories, which is slightly different from -s.
- -k: Display the capacity in KBytes;
- -m: Display the capacity in MBytes;
[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 you enter du directly without adding any options, du will analyze the files and directories in the current directory. The hard disk space occupied. Example 2Also list the capacity of the 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 3Check 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 /varwildcard * to represent each directory.
Different from df, the du command will actually search for all file data directly in the file system.
fdisk
fdisk is a Linux disk partition table operation tool.
Syntax:
fdisk [-l] 装置名称
Options and parameters:
-l: Output the contents of all partitions of the following devices. If there is only fdisk -l, Then the system will list all the partitions of the device that can be searched 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 out the disk where the root directory of your system is located , and check the relevant information in the 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 following command introduction
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)
Press q when leaving fdisk, then all None of the actions will take effect! On the contrary, pressing w means the action takes 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 and that’s it! Don't press w casually!
Use p to list the current partition table information of this disk. The upper half of this information displays the status of the overall disk.
Disk formatting
After the disk is divided, it is natural to format the file system. The formatting command is very simple. Use mkfs(make filesystem) command.
Syntax:
mkfs [-t 文件系统格式] 装置文件名
Options and parameters:
-t: Can be connected to file system formats, such as ext3, ext2, vfat, etc. (the system has Support will take effect)
Example 1
Check the file formats supported by mkfs
[root@www ~]# mkfs[tab][tab] mkfs mkfs.cramfs mkfs.ext2 mkfs.ext3 mkfs.msdos mkfs.vfat
Press two [tabs] and you will find that mkfs supports The file format is shown above.
Example 2
Format the partition /dev/hdc6 (you can specify your own partition) into 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 verification
fsck (file system check) is used to check and maintain inconsistent file systems.
If the system loses power or a disk problem occurs, you can use the fsck command to check the file system.
Syntax:
fsck [-t 文件系统] [-ACay] 装置名称
Options and parameters:
-t: The type of the given file system, if it already exists in /etc/fstab There is no need to add this parameter if it is defined or supported by the kernel itself.
-s: Execute fsck commands one by one in order to check
-A: Check all partitions listed in /etc/fstab
-C: Display the complete check progress
-
-d: Print out the debug results of e2fsck
-p: When there is the -A condition at the same time, multiple fsck checks are executed at the same time
-R: Omit/not check when -A condition is present at the same time
-V: Detailed display mode
- a: If there is an error in the check, it will be repaired automatically
-r: If there is an error in the check, the user will answer whether to repair it
-y: The option specifies that each file to be detected is automatically entered as yes. When you are not sure which ones are abnormal, you can execute #fsck -y to check and repair all.
Example 1
Check how many file systems the system supports fsck command:
[root@www ~]# fsck[tab][tab] fsck fsck.cramfs fsck.ext2 fsck.ext3 fsck.msdos fsck.vfat
Example 2
Forced detection of /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 there has never been a problem with this file system, the check process is very fast ! If you add -f to force checking, the process will be displayed one by one.
Disk mounting and unmounting
To mount a Linux disk, use the mount command, and to uninstall it, use the umount command.
Disk mount 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 /dev/hdc6 just created 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 command umount Syntax:
umount [-fn] 装置文件名或挂载点
Options and parameters:
-f: Forced dismount! Can be used in situations where the Network File System (NFS) cannot be read;
-n: Uninstall without upgrading /etc/mtab.
Uninstall /dev/hdc6
[root@www ~]# umount /dev/hdc6
