Linux Disk Management

Linux Disk Management

Linux Disk Management is directly related to the performance of the whole system.

Linux Disk Management commonly uses three commands for DF, Du, and Fdisk.

• DF: List The overall disk usage of the file system
• Du: Check Disk space usage
• FDISK: For disk partitioning

Df

DF Command parameter function: Check the disk space consumption of the file system. You can use this command to get information about how much space the hard disk is taking up, and how much space is left.

Grammar:

df [-ahikHTm] [目录或文件名]

Options :

Options	Description
-A or--all	Contains all the file systems;
--block-size= <区块大小>	Displays the number of chunks in the specified chunk size;
-H or--human-readable	Display information in a more readable manner;
-H or--si	Same as-h parameter, but is calculated as the unit of Bytes instead of the Bytes;
-I. or--inodes	Displays information about the inode;
-K or--kilobytes	The specified chunk size is 1024 bytes;
-L or--local	Only the local file system is displayed;
-M or--megabytes	The specified chunk size is 1048576 bytes;
--no-sync	Do not perform the sync instruction until the disk usage information is obtained, this is a preset value;
-P or--portability	Use the POSIX output format;
--sync	Before obtaining the disk usage information, perform the sync instruction first;
-T <文件系统类型> or <文件系统类型> --type=	Displays only disk information for the specified file system type;
-T or--print-type	Displays the type of file system;
-X <文件系统类型> or <文件系统类型> --exclude-type=	Do not display disk information for the specified file system type;
--help	Display Help;
--version	Displays version information.

Example 1

List all the file systems in the system!

[[email protected] ~]# df文件系统                   1K-块    已用     可用 已用% 挂载点/dev/mapper/centos-root 17811456 1318704 16492752    8% /devtmpfs                  488788       0   488788    0% /devtmpfs                     499848       0   499848    0% /dev/shmtmpfs                     499848    6808   493040    2% /runtmpfs                     499848       0   499848    0% /sys/fs/cgroup/dev/sda1                1038336  127464   910872   13% /boottmpfs                      99972       0    99972    0% /run/user/0

Under Linux If DF does not have any options, the default is to list all of the system's (non-special in-memory file systems and Swaps) in 1 Kbytes capacity!

Example 2

Display capacity results in an easy-to-read capacity format

[[email protected] ~]# df -h文件系统                 容量  已用  可用 已用% 挂载点/dev/mapper/centos-root   17G  1.3G   16G    8% /devtmpfs                 478M     0  478M    0% /devtmpfs                    489M     0  489M    0% /dev/shmtmpfs                    489M  6.7M  482M    2% /runtmpfs                    489M     0  489M    0% /sys/fs/cgroup/dev/sda1               1014M  125M  890M   13% /boottmpfs                     98M     0   98M    0% /run/user/0

Example 3

List all special file formats and names in the system

[[email protected] ~]# df -aTFilesystem    Type 1K-blocks    Used Available Use% Mounted on/dev/hdc2     ext3   9920624 3823112   5585444  41% /proc          proc         0       0         0   -  /procsysfs        sysfs         0       0         0   -  /sysdevpts      devpts         0       0         0   -  /dev/pts/dev/hdc3     ext3   4956316  141376   4559108   4% /home/dev/hdc1     ext3    101086   11126     84741  12% /boottmpfs        tmpfs    371332       0    371332   0% /dev/shmnone   binfmt_misc         0       0         0   -  /proc/sys/fs/binfmt_miscsunrpc  rpc_pipefs         0       0         0   -  /var/lib/nfs/rpc_pipefs

Example 4

Displays the available disk capacity under/etc in an easy-to-read capacity format

[[email protected] ~]# df -h /etcFilesystem            Size  Used Avail Use% Mounted on/dev/hdc2             9.5G  3.7G  5.4G  41% /

Du

The Linux du command also looks at the use of space, but unlike the DF command, the Linux du command is a view of the space used by the file and directory disks, or some difference from the DF command, which describes the Linux du command.

Grammar:

du [-ahskm] 文件或目录名称

Options :

Options	Description
-A or-all	Displays the size of individual files in the directory.
-B or-bytes	When the directory or file size is displayed, in bytes.
-C or--total	Displays the sum of all directories or files in addition to the size of individual directories or files.
-K or--kilobytes	Output in kilobytes (1024bytes).
-M or--megabytes	Output in megabytes.
-S or--summarize	Only totals are displayed, and only the last plus total value is listed.
-H or--human-readable	The readability of the information is improved by using K,M,G as the unit.
-X or--one-file-xystem	The file system at the beginning of processing, if encountered in other different file system directory is skipped.
-L <符号链接> or <符号链接> --dereference	Displays the source file size of the symbolic link specified in the options.
-S or--separate-dirs	When displaying the size of an individual directory, it does not contain the size of its subdirectories.
-X <文件> or <文件> --exclude-from=	In the <文件> specified directory or file.
--exclude= <目录或文件>	Skips over the specified directory or file.
-D or--dereference-args	Displays the source file size for the specified symbolic link.
-H or--si	The same as the-h parameter, but the k,m,g is converted to 1000 units.
-L or--count-links	Duplicate the hardware linked file.

Example 1

List all file sizes in the current directory

[[email protected] ~]# du8       ./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 direct input du does not have any options, du parses the hard disk space occupied by the files and directories in the directory that is currently located.

Example 2

The capacity of the file is also listed

[[email protected] ~]# du -a12      ./install.log.syslog   <==有文件的列表了8       ./.bash_logout8       ./test48       ./test2....中间省略....12      ./.gconfd220     .

Example 3

Check the capacity of each directory under the root directory

[[email protected] ~]# du -sm /*7       /bin6       /boot.....中间省略....0       /proc.....中间省略....1       /tmp3859    /usr     <==系统初期最大就是他了啦！77      /var

Wildcard characters * to represent each directory.

Unlike DF, du is a command that actually searches the file system for all of the file data.

Fdisk

FDISK is a disk partition table manipulation tool for Linux.

Grammar:

fdisk [-l] 装置名称

Options:

Options	Description
-B <分区大小>	Specify the size of each partition;
-L	Lists the partition table status for the specified peripheral device;
-S <分区编号>	Outputs the specified partition size to the standard output, in chunks;
-U	With the "-L" parameter list, the number of partitions is replaced by the number of columns to represent the starting address of each partition;
-V	Displays version information.

Example 1

List all partition information

[[email protected] ~]# fdisk -lDisk /dev/xvda: 21.5 GB, 21474836480 bytes255 heads, 63 sectors/track, 2610 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisk identifier: 0x00000000    Device Boot      Start         End      Blocks   Id  System/dev/xvda1   *           1        2550    20480000   83  Linux/dev/xvda2            2550        2611      490496   82  Linux swap / SolarisDisk /dev/xvdb: 21.5 GB, 21474836480 bytes255 heads, 63 sectors/track, 2610 cylindersUnits = cylinders of 16065 * 512 = 8225280 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisk identifier: 0x56f40944    Device Boot      Start         End      Blocks   Id  System/dev/xvdb2               1        2610    20964793+  83  Linux

Example 2

Locate the disk in the root directory on your system and check the relevant information on that drive.

[[email protected] ~]# 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% /[[email protected] ~]# 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 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)

Press when you leave Fdisk q , and all actions will not take effect! On the contrary, it w means that 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

Do you want to leave without saving? Press Q on the right! Don't just press W!

Using the p split table information that can list the current disk, the top half of this information displays the status of the overall disk.

Disk Formatting (MKFS)

After the disk is split, it is natural to format the file system, the format of the command is very simple, using the mkfs (make filesystem) command.

Syntax :

mkfs [-t 文件系统格式] 装置文件名

Options :

Options	Description
Fs	Specifies the parameters when the file system is established;
-T <文件系统类型>	Specify what file system to build;
-V	Display version information and detailed use method;
-V	Show a brief use method;
-C	Before making the file system, check whether the partition has a bad track.

Example 1

View supported file formats for MKFS

[[email protected] ~]# mkfs[tab][tab]mkfs         mkfs.cramfs  mkfs.ext2    mkfs.ext3    mkfs.msdos   mkfs.vfat

Pressing two [tab] will find the file format supported by MKFS as shown above.

Example 2

Format the partition/dev/hdc6 (you can specify your own partition) as the Ext3 file system:

[[email protected] ~]# mkfs -t ext3 /dev/hdc6mke2fs 1.39 (29-May-2006)Filesystem label=                <==这里指的是分割槽的名称(label)OS type: LinuxBlock 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 userFirst data block=0Maximum filesystem blocks=51589939216 block groups32768 blocks per group, 32768 fragments per group15712 inodes per groupSuperblock backups stored on blocks:        32768, 98304, 163840, 229376, 294912Writing inode tables: doneCreating journal (8192 blocks): done <==有日志记录Writing superblocks and filesystem accounting information: doneThis filesystem will be automatically checked every 34 mounts or180 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 inspection

The fsck (file system check) is used to check and maintain inconsistent file systems.

If the system is out of power or a disk problem occurs, the fsck command can be used to check the file system.

Grammar:

fsck [-t 文件系统] [-ACay] 装置名称

Options and Parameters:

Options	Description
-A	Automatically repair the file system without asking any questions;
-A	According to the contents of the/etc/fstab configuration file, check all the file system listed in the file;
-N	Does not execute the instruction, only lists the action which the actual execution will carry on;
-P	When used with the "-A" parameter, all file systems are checked at the same time;
-R	Use interactive mode to ask questions when performing a repair, allowing the user to confirm and determine the processing mode;
-R	When used with the "-A" parameter, the file system will skip/directory is not checked;
-S	Perform inspection operations sequentially, rather than concurrently;
-T <文件系统类型>	Specifies the type of file system to check;
-T	When the fsck command is executed, the header information is not displayed;
-V	Displays the instruction execution process.
-Y	The option specifies to detect that each file is automatically entered Yes and can perform a # fsck-y full check fix when unsure of those that are not normal.

Example 1

See how many file system support FSCK commands the system has:

[[email protected] ~]# fsck[tab][tab]fsck         fsck.cramfs  fsck.ext2    fsck.ext3    fsck.msdos   fsck.vfat

Example 2

To force detection of/DEV/HDC6 partitions:

[[email protected] ~]# 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 sizesPass 2: Checking directory structurePass 3: Checking directory connectivityPass 4: Checking reference countsPass 5: Checking group summary informationvbird_logical: 11/251968 files (9.1% non-contiguous), 36926/1004046 blocks

If you do not add-f option, because this file system has not been the problem, the check is very fast! If you add the-f mandatory Check, an item is displayed.

Disk mount and dismount

Linux Disk mounts use mount commands to uninstall the use umount command.

The Mount command is used to load the file system to the specified mount point. The most common use of this command is to mount the CDROM so that we can access the data in the CDROM because you insert the disc into the CDROM, Linux does not mount automatically, and you must manually complete the mount using the Linux mount command.

Disk mount Syntax:

mount [-t vfstype] [-o options] device dirmount [-t 文件系统] [-L Label名] [-o 额外选项] [-n]  装置文件名  挂载点

- t verbose options:

? Disc or disc Image: iso9660

? DOS FAT16 file system: MSDOS

? Windows 9x FAT32 file system: VFAT

? Windows NT NTFS file system: NTFS

? Mount Windows file network share: SMBFS (requires kernel support) Recommended CIFS

? UNIX (LINUX) file network share: NFS

- o verbose options:

? Loop: Used to attach a file as a hard disk partition on the system

? RO: Hook device with read-only method

? RW: Mount device with read-write mode

? Iocharset: Specifies the character set used to access the file system, such as Iocharset=utf8

? Remount: Re-mount

Example 1

In the default way, mount the/dev/hdc6 you just created onto/MNT/HDC6!

[[email protected] ~]# mkdir /dev/hdc6[[email protected] ~]# mount /dev/hdc6 /mnt/hdc6[[email protected] ~]# dfFilesystem           1K-blocks      Used Available Use% Mounted on.....中间省略...../dev/hdc6              1976312     42072   1833836   3% /mnt/hdc6

Disk Offload Command Umount

Grammar:

umount [-fn] 装置文件名或挂载点

Options and Parameters:

• -F: Forced removal! can be used in situations such as a network file system (NFS) that cannot be read;
• -N: Dismount without upgrading/etc/mtab.

Uninstalling/DEV/HDC6

[[email protected] ~]# umount /dev/hdc6    

Linux Disk Management