第5周

在腳本中使用fdisk

[root@CENTOS7 ~]#echo -e “n\n\n\n\n+1G\nw\n” | fdisk /dev/sdc
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 0x4c45a428.

Command (m for help): Partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
Select (default p): Using default response p
Partition number (1-4, default 1): First sector (2048-167772159, default 2048): Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-167772159, default 167772159): Partition 1 of type Linux and of size 1 GiB is set

Command (m for help): The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@CENTOS7 ~]#lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 200G 0 disk
├─sda1 8:1 0 1G 0 part /boot
├─sda2 8:2 0 50G 0 part /
├─sda3 8:3 0 30G 0 part /data
├─sda4 8:4 0 1K 0 part
├─sda5 8:5 0 2G 0 part [SWAP]
└─sda6 8:6 0 1G 0 part
sdb 8:16 0 100G 0 disk
├─sdb1 8:17 0 1G 0 part
├─sdb2 8:18 0 1K 0 part
├─sdb3 8:19 0 2G 0 part
└─sdb5 8:21 0 200M 0 part
sdc 8:32 0 80G 0 disk
└─sdc1 8:33 0 1G 0 part
sdd 8:48 0 60G 0 disk
sr0 11:0 1 8.1G 0 rom /run/media/root/CentOS 7 x86_64

[root@CENTOS7 ~]#echo -e “n\n\n\n\n+1G\nw\n” | fdisk /dev/sdc 從定向方式
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 0x4c45a428.

Command (m for help): Partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
Select (default p): Using default response p
Partition number (1-4, default 1): First sector (2048-167772159, default 2048): Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-167772159, default 167772159): Partition 1 of type Linux and of size 1 GiB is set

Command (m for help): The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@CENTOS7 ~]#lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 200G 0 disk
├─sda1 8:1 0 1G 0 part /boot
├─sda2 8:2 0 50G 0 part /
├─sda3 8:3 0 30G 0 part /data
├─sda4 8:4 0 1K 0 part
├─sda5 8:5 0 2G 0 part [SWAP]
└─sda6 8:6 0 1G 0 part
sdb 8:16 0 100G 0 disk
├─sdb1 8:17 0 1G 0 part
├─sdb2 8:18 0 1K 0 part
├─sdb3 8:19 0 2G 0 part
└─sdb5 8:21 0 200M 0 part
sdc 8:32 0 80G 0 disk
└─sdc1 8:33 0 1G 0 part
sdd 8:48 0 60G 0 disk
sr0 11:0 1 8.1G 0 rom /run/media/root/CentOS 7 x86_64

查看centos6上sda有多少個塊組，一個塊組就多少個塊組成
dumpe2fs /dev/sda1

[root@centos ~]#dumpe2fs /dev/sda1
dumpe2fs 1.41.12 (17-May-2010)
Filesystem volume name: <none>
Last mounted on: /boot
Filesystem UUID: 414ab9ee-af40-44f1-b300-d29fc674eb8e
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 65536
Block count: 262144
Reserved block count: 13107
Free blocks: 241094
Free inodes: 65498
First block: 0
Block size: 4096
Fragment size: 4096
Reserved GDT blocks: 63
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 8192
Inode blocks per group: 512
Flex block group size: 16
Filesystem created: Tue Mar 27 16:56:37 2018
Last mount time: Mon Apr 23 08:47:13 2018
Last write time: Mon Apr 23 08:47:13 2018
Mount count: 52
Maximum mount count: -1
Last checked: Tue Mar 27 16:56:37 2018
Check interval: 0 (<none>)
Lifetime writes: 82 MB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: 1ae4dcb2-74ba-4214-955b-ae990ad39f42
Journal backup: inode blocks
Journal features: (none)
Journal size: 32M
Journal length: 8192
Journal sequence: 0x00000038
Journal start: 0

Group 0: (Blocks 0-32767) [ITABLE_ZEROED]
Checksum 0xf60c, unused inodes 8155
Primary superblock at 0, Group descriptors at 1-1
Reserved GDT blocks at 2-64
Block bitmap at 65 (+65), Inode bitmap at 81 (+81)
Inode table at 97-608 (+97)
28581 free blocks, 8155 free inodes, 5 directories, 8155 unused inodes
Free blocks: 79, 90-95, 4194-32767
Free inodes: 38-8192
Group 1: (Blocks 32768-65535) [ITABLE_ZEROED]
Checksum 0x2122, unused inodes 8191
Backup superblock at 32768, Group descriptors at 32769-32769
Reserved GDT blocks at 32770-32832
Block bitmap at 66 (+4294934594), Inode bitmap at 82 (+4294934610)
Inode table at 609-1120 (+4294935137)
24292 free blocks, 8191 free inodes, 1 directories, 8191 unused inodes
Free blocks: 34666-34667, 34682-34683, 34688-34815, 41362-41363, 41374-41375, 41380-65535
Free inodes: 8194-16384
Group 2: (Blocks 65536-98303) [INODE_UNINIT, BLOCK_UNINIT, ITABLE_ZEROED]
Checksum 0x4789, unused inodes 8192
Block bitmap at 67 (+4294901827), Inode bitmap at 83 (+4294901843)
Inode table at 1121-1632 (+4294902881)
32768 free blocks, 8192 free inodes, 0 directories, 8192 unused inodes
Free blocks: 65536-98303
Free inodes: 16385-24576
Group 3: (Blocks 98304-131071) [INODE_UNINIT, ITABLE_ZEROED]
Checksum 0x30dc, unused inodes 8192
Backup superblock at 98304, Group descriptors at 98305-98305
Reserved GDT blocks at 98306-98368
Block bitmap at 68 (+4294869060), Inode bitmap at 84 (+4294869076)
Inode table at 1633-2144 (+4294870625)
32703 free blocks, 8192 free inodes, 0 directories, 8192 unused inodes
Free blocks: 98369-131071
Free inodes: 24577-32768
Group 4: (Blocks 131072-163839) [INODE_UNINIT, ITABLE_ZEROED]
Checksum 0x74e6, unused inodes 8192
Block bitmap at 69 (+4294836293), Inode bitmap at 85 (+4294836309)
Inode table at 2145-2656 (+4294838369)
24576 free blocks, 8192 free inodes, 0 directories, 8192 unused inodes
Free blocks: 139264-163839
Free inodes: 32769-40960
Group 5: (Blocks 163840-196607) [INODE_UNINIT, ITABLE_ZEROED]
Checksum 0x0de1, unused inodes 8192
Backup superblock at 163840, Group descriptors at 163841-163841
Reserved GDT blocks at 163842-163904
Block bitmap at 70 (+4294803526), Inode bitmap at 86 (+4294803542)
Inode table at 2657-3168 (+4294806113)
32703 free blocks, 8192 free inodes, 0 directories, 8192 unused inodes
Free blocks: 163905-196607
Free inodes: 40961-49152
Group 6: (Blocks 196608-229375) [INODE_UNINIT, BLOCK_UNINIT, ITABLE_ZEROED]
Checksum 0x44e3, unused inodes 8192
Block bitmap at 71 (+4294770759), Inode bitmap at 87 (+4294770775)
Inode table at 3169-3680 (+4294773857)
32768 free blocks, 8192 free inodes, 0 directories, 8192 unused inodes
Free blocks: 196608-229375
Free inodes: 49153-57344
Group 7: (Blocks 229376-262143) [INODE_UNINIT, ITABLE_ZEROED]
Checksum 0x4c72, unused inodes 8192
Backup superblock at 229376, Group descriptors at 229377-229377
Reserved GDT blocks at 229378-229440
Block bitmap at 72 (+4294737992), Inode bitmap at 88 (+4294738008)
Inode table at 3681-4192 (+4294741601)
32703 free blocks, 8192 free inodes, 0 directories, 8192 unused inodes
Free blocks: 229441-262143
Free inodes: 57345-65536

superblock 很重要其中存放著分區的元數據和塊組的劃分，所以在奇數1，3..9….都有備份

[root@CENTOS7 ~]#mkfs.ext4 /dev/sdc1 -b 1024 創建一個文件系統指定這個文件系統的塊大小是1k，塊的大小只有在創建文件系統的時候可以指定，一但創建完畢則無法修改。默認的是4k
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
65536 inodes, 1048576 blocks
52428 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=34603008
128 block groups
8192 blocks per group, 8192 fragments per group
512 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409, 663553,
1024001

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

[root@CENTOS7 ~]#tune2fs -l /dev/sdc1
tune2fs 1.42.9 (28-Dec-2013)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: e3982c14-ce5c-4285-8fb0-26816d691b6e
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 65536
Block count: 1048576
Reserved block count: 52428
Free blocks: 996238
Free inodes: 65525
First block: 1
Block size: 1024
Fragment size: 1024
Group descriptor size: 64
Reserved GDT blocks: 256
Blocks per group: 8192
Fragments per group: 8192
Inodes per group: 512
Inode blocks per group: 128
Flex block group size: 16
Filesystem created: Mon Apr 23 19:35:25 2018
Last mount time: n/a
Last write time: Mon Apr 23 19:35:25 2018
Mount count: 0
Maximum mount count: -1
Last checked: Mon Apr 23 19:35:25 2018
Check interval: 0 (<none>)
Lifetime writes: 32 MB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: 74c87523-34f1-4be2-864c-d515d4425a22
Journal backup: inode blocks

Inode count: 65536 節點編號
Block count: 1048576 塊數量
Reserved block count: 52428 默認百分之5，保留的塊數量留給id為0的用戶使用
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)

mkfs.ext4 /dev/sdc1 -b 1024 -m 1
mke2fs：ext系列文件系統專用管理工具
-t {ext2|ext3|ext4}
-b {1024|2048|4096}
-L ‘LABEL’
-j: 相當于 -t ext3
mkfs.ext3 = mkfs -t ext3 = mke2fs -j = mke2fs -t ext3
-i #: 為數據空間中每多少個字節創建一個inode；此大小
不應該小于block的大小
-N #：指定分區中創建多少個inode
-I 一個inode記錄占用的磁盤空間大小，128—4096
-m #: 默認5%,為管理人員預留空間占總空間的百分比
-O FEATURE[,…]：啟用指定特性
-O ^FEATURE：關閉指定特性

[root@CENTOS7 ~]#mkfs.ext4 /dev/sdc1 -b 1024 -m 0.1 創建一個塊是1k，為id0預留千分之一個塊的文件系統
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
65536 inodes, 1048576 blocks
1048 blocks (0.10%) reserved for the super user
First data block=1
Maximum filesystem blocks=34603008
128 block groups
8192 blocks per group, 8192 fragments per group
512 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409, 663553,
1024001

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

[root@CENTOS7 ~]#tune2fs -l /dev/sdc1
tune2fs 1.42.9 (28-Dec-2013)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 884dac1d-3d83-4685-8b98-53bcb1619452
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 65536
Block count: 1048576
Reserved block count: 1048
Free blocks: 996238
Free inodes: 65525
First block: 1
Block size: 1024
Fragment size: 1024
Group descriptor size: 64
Reserved GDT blocks: 256
Blocks per group: 8192
Fragments per group: 8192
Inodes per group: 512
Inode blocks per group: 128
Flex block group size: 16
Filesystem created: Mon Apr 23 19:42:10 2018
Last mount time: n/a
Last write time: Mon Apr 23 19:42:11 2018
Mount count: 0
Maximum mount count: -1
Last checked: Mon Apr 23 19:42:10 2018
Check interval: 0 (<none>)
Lifetime writes: 32 MB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: 0940f0ee-880e-40a1-bc8c-21bb6677114a
Journal backup: inode blocks

[root@CENTOS7 ~]#mkfs.ext4 /dev/sdc2 -b 1024 -i 1024 -m 1
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
2097152 inodes, 2097152 blocks
20971 blocks (1.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=35651584
256 block groups
8192 blocks per group, 8192 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409, 663553,
1024001, 1990657

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

[root@CENTOS7 ~]#tune2fs -l /dev/sdc2
tune2fs 1.42.9 (28-Dec-2013)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 381e389c-a0a7-4b8d-bc7e-5c29152162ce
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 2097152
Block count: 2097152
Reserved block count: 20971
Free blocks: 1536293
Free inodes: 2097141
First block: 1
Block size: 1024
Fragment size: 1024
Group descriptor size: 64
Reserved GDT blocks: 256
Blocks per group: 8192
Fragments per group: 8192
Inodes per group: 8192
Inode blocks per group: 2048
Flex block group size: 16
Filesystem created: Mon Apr 23 19:48:03 2018
Last mount time: n/a
Last write time: Mon Apr 23 19:48:04 2018
Mount count: 0
Maximum mount count: -1
Last checked: Mon Apr 23 19:48:03 2018
Check interval: 0 (<none>)
Lifetime writes: 32 MB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: f5054342-a203-4d51-b668-67f26b90ae0e
Journal backup: inode blocks

[root@CENTOS7 ~]#mkfs.ext4 /dev/sdc2 -N 209715 指定多少個inodes，實際要多一些可能是因為取整.
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
209920 inodes, 524288 blocks
26214 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=536870912
16 block groups
32768 blocks per group, 32768 fragments per group
13120 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912

Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done

[root@CENTOS7 ~]#tune2fs -l /dev/sdc2
tune2fs 1.42.9 (28-Dec-2013)
Filesystem volume name: <none>
Last mounted on: <not available>
Filesystem UUID: 60be96b2-617c-4a8d-90f4-4f6fe194333e
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 209920
Block count: 524288
Reserved block count: 26214
Free blocks: 493204
Free inodes: 209909
First block: 0
Block size: 4096
Fragment size: 4096
Group descriptor size: 64
Reserved GDT blocks: 255
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 13120
Inode blocks per group: 820
Flex block group size: 16
Filesystem created: Mon Apr 23 19:55:26 2018
Last mount time: n/a
Last write time: Mon Apr 23 19:55:27 2018
Mount count: 0
Maximum mount count: -1
Last checked: Mon Apr 23 19:55:26 2018
Check interval: 0 (<none>)
Lifetime writes: 65 MB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: e3845910-09be-4b48-a8e4-aef809454480
Journal backup: inode blocks

[root@CENTOS7 ~]#mkfs.ext2 /dev/sdc1 -O has_journal 添加日志功能
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
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

Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

[root@CENTOS7 ~]#blkid /dev/sdc1
/dev/sdc1: UUID=”34cacf85-0038-42c5-9ce5-0d77bba36d43″ SEC_TYPE=”ext2″ TYPE=”ext3″

[root@CENTOS7 ~]#tune2fs -O ^has_journal /dev/sdc1 取消日志功能
tune2fs 1.42.9 (28-Dec-2013)
[root@CENTOS7 ~]#blkid /dev/sdc1
/dev/sdc1: UUID=”8980fe3c-2c14-4db8-b623-b4f0bfcc3cba” TYPE=”ext2″

[root@CENTOS7 ~]#mkfs.ext4 /dev/sdc1 -L data 創建文件系統時起（卷標），最好用掛載點的名字
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=data
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

Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done

[root@CENTOS7 ~]#tune2fs -l /dev/sdc1
tune2fs 1.42.9 (28-Dec-2013)
Filesystem volume name: data

[root@CENTOS7 ~]#blkid /dev/sdc1
/dev/sdc1: LABEL=”data” UUID=”70496471-2329-49d7-8524-5ba956fbb040″ TYPE=”ext4″

文件系統標簽
指向設備的另一種方法
與設備無關
blkid：塊設備屬性信息查看
blkid [OPTION]… [DEVICE]
-U UUID: 根據指定的UUID來查找對應的設備 通用

-L LABEL：根據指定的LABEL來查找對應的設備
e2label：管理ext系列文件系統的LABEL
e2label DEVICE [LABEL] 只適合ext系列
findfs ：查找分區
findfs [options] LABEL=<label> 通用
findfs [options] UUID=<uuid>

[root@CENTOS7 ~]#blkid -U c837ab44-edcb-43af-b4fa-c26832a7af7e 用uuid查看設備名
/dev/sdb1

[root@CENTOS7 ~]#blkid -L “data” 用卷標查看設備名
/dev/sdc1

[root@centos ~]#cat /etc/fstab

#
# /etc/fstab
# Created by anaconda on Tue Mar 27 16:59:39 2018
#
# Accessible filesystems, by reference, are maintained under ‘/dev/disk’
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=408b65d7-7551-480b-8916-5eff4cca1b00 / ext4 defaults 1 1
UUID=414ab9ee-af40-44f1-b300-d29fc674eb8e /boot ext4 defaults 1 2
UUID=37d5cf25-ead4-427b-9655-40fc1602b5df /data ext4 defaults 1 2
UUID=9fc26932-7094-4948-b395-24ab05d8ea73 swap swap defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
[root@centos ~]#cat /etc/fstab | grep -o “data”
data
[root@centos ~]#cat /etc/fstab | grep “data”
UUID=37d5cf25-ead4-427b-9655-40fc1602b5df /data ext4 defaults 1 2
[root@centos ~]#cat /etc/fstab | grep “data” | sed -r ‘s@.*=(.*) /.*@\1@’
37d5cf25-ead4-427b-9655-40fc1602b5df
[root@centos ~]#blkid -U `cat /etc/fstab | grep “data” | sed -r ‘s@.*=(.*) /.*@\1@’` 查看data對應的設備名
/dev/sda3

root@CENTOS7 ~]#e2label /dev/sdc1 /data/sdc1 修改卷標名字 只識別ext4
[root@CENTOS7 ~]#e2label /dev/sdc1
/data/sdc1

[root@CENTOS7 ~]#findfs LABEL=/data/sdc1
/dev/sdc1

[root@CENTOS7 ~]#findfs UUID=”4d8d9214-eeed-4758-8c34-f05492b9ea73″
/dev/sda1

tune2fs
tune2fs：重新設定ext系列文件系統可調整參數的值
-l：查看指定文件系統超級塊信息；super block
-L ‘LABEL’：修改卷標
-m #：修預留給管理員的空間百分比
-j: 將ext2升級為ext3
-O: 文件系統屬性啟用或禁用, –O ^has_journal
-o: 調整文件系統的默認掛載選項，–o ^acl
-U UUID: 修改UUID號
dumpe2fs：
塊分組管理，32768塊
-h：查看超級塊信息，不顯示分組信息

/dev/sdc1: LABEL=”/data/sdc1″ UUID=”c2188236-fd12-4348-b372-7ee9003ae378″ TYPE=”ext4″
/dev/sdc2: UUID=”60be96b2-617c-4a8d-90f4-4f6fe194333e” TYPE=”ext4″
[root@CENTOS7 ~]#tune2fs -U `uuidgen` /dev/sdc1 修改UUID，一般不要修改
tune2fs 1.42.9 (28-Dec-2013)
[root@CENTOS7 ~]#blkid
/dev/sdb1: UUID=”c837ab44-edcb-43af-b4fa-c26832a7af7e” TYPE=”ext4″
/dev/sdb3: UUID=”8eeacb99-2062-4604-89c5-6518d832bec8″ TYPE=”ext2″
/dev/sda1: UUID=”4d8d9214-eeed-4758-8c34-f05492b9ea73″ TYPE=”xfs”
/dev/sda2: UUID=”0a1bc23e-06e5-4210-9b32-0edbff09ca1a” TYPE=”xfs”
/dev/sda3: UUID=”fb669d84-551f-4a70-a11e-f61deec0fd86″ TYPE=”xfs”
/dev/sda5: UUID=”906330a5-2af1-4bf4-8b2d-9337eaf92250″ TYPE=”swap”
/dev/sr0: UUID=”2017-09-06-10-53-42-00″ LABEL=”CentOS 7 x86_64″ TYPE=”iso9660″ PTTYPE=”dos”
/dev/sdc1: LABEL=”/data/sdc1″ UUID=”ad468b62-a818-493d-911f-4f8a871986b9″ TYPE=”ext4″

文件系統檢測和修復
常發生于死機或者非正常關機之后
掛載為文件系統標記為“no clean”
注意：一定不要在掛載狀態下修復
fsck: File System Check
fsck.FS_TYPE
fsck -t FS_TYPE
-p: 自動修復錯誤
-r: 交互式修復錯誤
FS_TYPE一定要與分區上已經文件類型相同
e2fsck：ext系列文件專用的檢測修復工具
-y：自動回答為yes
-f：強制修復

[root@CENTOS7 ~]#dd if=/dev/zero of=/dev/sdc1 bs=1M count=20 破壞一個文件系統
20+0 records in
20+0 records out
20971520 bytes (21 MB) copied, 0.186818 s, 112 MB/s
[root@CENTOS7 ~]#tune2fs -l /dev/sdc1 已經破壞無法查看
tune2fs 1.42.9 (28-Dec-2013)
tune2fs: Bad magic number in super-block while trying to open /dev/sdc1
Couldn’t find valid filesystem superblock.
[root@CENTOS7 ~]#fsck /dev/sdc1 -y 修復
fsck from util-linux 2.23.2
e2fsck 1.42.9 (28-Dec-2013)
ext2fs_open2: Bad magic number in super-block
fsck.ext2: Superblock invalid, trying backup blocks…
Superblock has an invalid journal (inode 8).
Clear? yes

*** ext3 journal has been deleted – filesystem is now ext2 only ***

/data/sdc1 was not cleanly unmounted, check forced.
Resize inode not valid. Recreate? yes

Pass 1: Checking inodes, blocks, and sizes
Root inode is not a directory. Clear? yes

Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Root inode not allocated. Allocate? yes

/lost+found not found. Create? yes

Pass 4: Checking reference counts
Pass 5: Checking group summary information
Block bitmap differences: +(0–136) +(145–152) +(161–4257) +(32768–32896) +(98304–98432) +(163840–163968) +(229376–229504)
Fix? yes

Free blocks count wrong for group #0 (28519, counted=28524).
Fix? yes

Free blocks count wrong for group #4 (24576, counted=32768).
Fix? yes

Free blocks count wrong (249187, counted=257384).
Fix? yes

Inode bitmap differences: +1 +(3–10)
Fix? yes

Free inodes count wrong for group #0 (8180, counted=8181).
Fix? yes

Directories count wrong for group #0 (3, counted=2).
Fix? yes

Free inodes count wrong (65524, counted=65525).
Fix? yes

Recreate journal? yes

Creating journal (8192 blocks): Done.

*** journal has been re-created – filesystem is now ext3 again ***

/data/sdc1: ***** FILE SYSTEM WAS MODIFIED *****
/data/sdc1: 11/65536 files (0.0% non-contiguous), 12952/262144 blocks
[root@CENTOS7 ~]#tune2fs -l /dev/sdc1 修復成功顯示為clean
tune2fs 1.42.9 (28-Dec-2013)
Filesystem volume name: /data/sdc1
Last mounted on: <not available>
Filesystem UUID: ad468b62-a818-493d-911f-4f8a871986b9
Filesystem magic number: 0xEF53
Filesystem revision #: 1 (dynamic)
Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags: signed_directory_hash
Default mount options: user_xattr acl
Filesystem state: clean
Errors behavior: Continue
Filesystem OS type: Linux
Inode count: 65536
Block count: 262144
Reserved block count: 13107
Free blocks: 249192
Free inodes: 65525
First block: 0
Block size: 4096
Fragment size: 4096
Group descriptor size: 64
Reserved GDT blocks: 127
Blocks per group: 32768
Fragments per group: 32768
Inodes per group: 8192
Inode blocks per group: 512
Flex block group size: 16
Filesystem created: Mon Apr 23 20:11:09 2018
Last mount time: n/a
Last write time: Mon Apr 23 20:46:23 2018
Mount count: 0
Maximum mount count: -1
Last checked: Mon Apr 23 20:46:23 2018
Check interval: 0 (<none>)
Lifetime writes: 65 MB
Reserved blocks uid: 0 (user root)
Reserved blocks gid: 0 (group root)
First inode: 11
Inode size: 256
Required extra isize: 28
Desired extra isize: 28
Journal inode: 8
Default directory hash: half_md4
Directory Hash Seed: bfa8a27e-378a-4cdc-8184-6a2dd5f92ac6
Journal backup: inode blocks

[root@CENTOS7 ~]#e2fsck -f /dev/sdc1 強制檢查全盤文件系統
e2fsck 1.42.9 (28-Dec-2013)
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
/data/sdc1: 11/65536 files (0.0% non-contiguous), 12952/262144 blocks

在centos7上修復文件系統用的命令是

xfs_repair

[root@CENTOS7 ~]#xfs_ 雙擊Tan查看覺得其他功能
xfs_admin xfs_db xfs_fsr xfs_io xfs_metadump xfs_quota
xfs_bmap xfs_estimate xfs_growfs xfs_logprint xfs_mkfile xfs_repair
xfs_copy xfs_freeze xfs_info xfs_mdrestore xfs_ncheck xfs_rtcp

[root@CENTOS7 ~]#xfs_info /dev/sda3 顯示信息 但是必須是掛載狀態才能查詢
meta-data=/dev/sda3 isize=512 agcount=4, agsize=1966080 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0 spinodes=0
data = bsize=4096 blocks=7864320, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal bsize=4096 blocks=3840, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0

掛載mount
掛載:將額外文件系統與根文件系統某現存的目錄建立起關聯關系，進而使得此
目錄做為其它文件訪問入口的行為
卸載:為解除此關聯關系的過程
把設備關聯掛載點：mount Point
mount
卸載時：可使用設備，也可以使用掛載點
umount
掛載點下原有文件在掛載完成后會被臨時隱藏
掛載點目錄一般為空
一個掛載點不能掛載多個設備。作為掛載點最好是空文件夾，如果不是空里面的文件會被掛載的設備遮蓋導致無法查看，但是文件沒有消失當取消掛載的時候還會顯示出來。一個設備可以掛載在多個掛載點上，掛載點顯示的文件內容是一樣的（比如光盤掛載在/misc和/run），有點像硬鏈接，但是連接數并不增多

用mount命令掛載文件系統
掛載方法：mount DEVICE MOUNT_POINT
mount：通過查看/etc/mtab文件顯示當前已掛載的所有設備
mount [-fnrsvw] [-t vfstype] [-o options] device dir
device：指明要掛載的設備；
(1) 設備文件：例如/dev/sda5
(2) 卷標：-L ‘LABEL’, 例如 -L ‘MYDATA’
(3) UUID, -U ‘UUID’：例如 -U ‘0c50523c-43f1-45e7-
85c0-a126711d406e’
(4) 偽文件系統名稱：proc, sysfs, devtmpfs, configfs
dir：掛載點
事先存在；建議使用空目錄
進程正在使用中的設備無法被卸載

[root@CENTOS7 data]#mkdir sdc1

[root@CENTOS7 ~]#mount /dev/sdc1 /data/sdc1

[root@CENTOS7 ~]#df

dev/sdc1 999320 2552 927956 1% /data/sdc1

[root@CENTOS7 ~]#mount

/dev/sdc1 on /data/sdc1 type ext4 (rw,relatime,seclabel,data=ordered)

[root@CENTOS7 ~]#ll /etc/mtab 掛載的信息存放的地方
lrwxrwxrwx. 1 root root 17 Apr 19 20:35 /etc/mtab -> /proc/self/mounts

[root@CENTOS7 ~]#umount /dev/sdc1 取消掛載，可以寫設備名，卷標
[root@CENTOS7 ~]#df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda2 52403200 3898416 48504784 8% /
devtmpfs 535296 0 535296 0% /dev
tmpfs 550036 0 550036 0% /dev/shm
tmpfs 550036 7964 542072 2% /run
tmpfs 550036 0 550036 0% /sys/fs/cgroup
/dev/sda3 31441920 161500 31280420 1% /data
/dev/sda1 1038336 161620 876716 16% /boot
tmpfs 110008 24 109984 1% /run/user/0
/dev/sr0 8490330 8490330 0 100% /run/media/root/CentOS 7 x86_64
tmpfs 110008 0 110008 0% /run/user/1000

[root@CENTOS7 ~]#umount LABEL=/data/sdc1

[root@CENTOS7 ~]#mount LABEL=/data/sdc1 /data/sdc1

[root@CENTOS7 ~]#mkdir /data/sdc11
[root@CENTOS7 ~]#mount /dev/sdc1 /data/sdc11
[root@CENTOS7 ~]#cd /data/sdc1
[root@CENTOS7 sdc1]#touch f1
[root@CENTOS7 sdc1]#ls
f1 lost+found
[root@CENTOS7 sdc1]#cd
[root@CENTOS7 ~]#cd /data/sdc11
[root@CENTOS7 sdc11]#ls
f1 lost+found

[root@CENTOS7 sdc1]#mount /dev/sdc2 /data/sdc1 多個設備掛載到同一個文件夾

[root@CENTOS7 sdc1]#ls
f1 lost+found
[root@CENTOS7 sdc1]#cd ..
[root@CENTOS7 data]#ls ./sdc1
lost+found

普通用戶沒有權限掛載，也沒有權限卸載掛載

[root@CENTOS7 data]#mount -r /dev/sdc2 /data/sdc2 只讀
[root@CENTOS7 data]#mount

/dev/sdc2 on /data/sdc2 type ext4 (ro,

[root@CENTOS7 sdc2]#mount -t ext2 /dev/sdc2 /data/sdc2
已ext2文件系統去掛載，除非有必要，不然系統會自動識別文件系統類型，不需要指明

mount常用命令選項
-t vsftype：指定要掛載的設備上的文件系統類型
-r: readonly，只讀掛載
-w: read and write, 讀寫掛載 默認就是可讀可寫
-n: 不更新/etc/mtab，mount不可見
-a：自動掛載所有支持自動掛載的設備(定義在了/etc/fstab文件中，且掛載選
項中有auto功能)
-L ‘LABEL’: 以卷標指定掛載設備
-U ‘UUID’: 以UUID指定要掛載的設備
-B, –bind: 綁定目錄到另一個目錄上
查看內核追蹤到的已掛載的所有設備
cat /proc/mounts

mount -n /dev/sdc2 /data/sdc2 只在centos6上好用

df cat/dtc/mtab mount查看不到，但是cat/proc/mounts可以查看

[root@CENTOS7 dir]#mount -B /data/dir /data/sdc2
[root@CENTOS7 dir]#touch /data/sdc2/ff
[root@CENTOS7 dir]#ls /data/dir
ff

mount常用命令選項
-o options：(掛載文件系統的選項)，多個選項使用逗號分隔
async：異步模式
sync：同步模式,內存更改時，同時寫磁盤
atime/noatime：包含目錄和文件
diratime/nodiratime：目錄的訪問時間戳
auto/noauto：是否支持自動掛載,是否支持-a選項
exec/noexec：是否支持將文件系統上運行應用程序
dev/nodev：是否支持在此文件系統上使用設備文件
suid/nosuid：是否支持suid和sgid權限
remount：重新掛載
ro：只讀
rw：讀寫
user/nouser：是否允許普通用戶掛載此設備，/etc/fstab使用
acl：啟用此文件系統上的acl功能
loop: 使用loop設備
defaults：相當于rw, suid, dev, exec, auto, nouser, async

Mount count: 4 當達到20次時會檢查
Maximum mount count: 20
Check interval: 0 (<none>) 到達指定時間檢查

[root@CENTOS7 ~]#tune2fs -c 20 /dev/sdc2 調整最大掛載次數，-C調整當前掛載次數
tune2fs 1.42.9 (28-Dec-2013)
Setting maximal mount count to 20

tune2fs -o acl /dev/sdc2 添加 acl權限
tune2fs -o ^acl /dev/sdc2 取消acl權限都需要從新掛載才能生效

mount -o acl /dev/sdc2 /data/sdc2 也可以添加acl權限

mount -o noacl,remount /dev/sdc2 /data/sdc2 不用卸載掛載，直接修改acl權限

卸載命令
查看掛載情況
findmnt MOUNT_POINT|device
查看正在訪問指定文件系統的進程
lsof MOUNT_POINT
fuser -v MOUNT_POINT
終止所有在正訪問指定的文件系統的進程
fuser -km MOUNT_POINT
卸載
umount DEVICE
umount MOUNT_POINT

[root@centos ~]#fuser -v /data/sdb1 查看誰在使用
USER PID ACCESS COMMAND
/data/sdb1: root 3543 ..c.. bash

[root@centos ~]#fuser -km /data/sdb1 結束所有正在訪問這個文件夾的進程
/data/sdb1: 3543c

[root@centos ~]#lsof /data/sdb1 查看誰在使用這個文件夾
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
bash 3574 root cwd DIR 8,17 4096 2 /data/sdb1

root@centos ~]#findmnt /dev/sdb1
TARGET SOURCE FSTYPE OPTIONS
/data/sdb1 /dev/sdb1 ext4 rw,relatime,seclabel,barrier=1,data=ordered

[root@centos ~]#findmnt /dev/sdb2 查看一個設備是否被掛載
[root@centos ~]#

[root@centos ~]#findmnt /data/sdb2 &>/dev/null || mount /dev/sdb2 /data/sdb2
[root@centos ~]#df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda2 50264772 5516120 42188652 12% /
tmpfs 502056 76 501980 1% /dev/shm
/dev/sda1 999320 34944 911948 4% /boot
/dev/sda3 30106576 99960 28470616 1% /data
/dev/sr0 3878870 3878870 0 100% /media/CentOS_6.9_Final
/dev/sdb1 1010780 1304 956464 1% /data/sdb1
/dev/sdb2 2005880 3096 1897560 1% /data/sdb2

[root@centos ~]#dd if=/dev/zero of=/root/p1 bs=1M count=100
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 4.87694 s, 21.5 MB/s
[root@centos ~]#mkfs.ext4 /root/p1
mke2fs 1.41.12 (17-May-2010)
/root/p1 is not a block special device.
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux

[root@centos ~]#mount /root/p1 /data/mm
mount: /root/p1 is not a block device (maybe try `-o loop’?)
[root@centos ~]#mount -o loop /root/p1 /data/mm 將一個文件模擬一個分區使用
[root@centos ~]#touch /data/mm/f1 在這個目錄下創建的文件都放在p1里面
想把p1里的所有文件移走直接卸載掛載，遠程復制到別的機器上，然后在掛載就可以將里面的文件導出來

[root@centos ~]#losetup -a 查看所有loop設備
/dev/loop0: [0802]:3014775 (/root/p1)

[root@centos ~]#ls /dev/loop*
/dev/loop0 /dev/loop1 /dev/loop2 /dev/loop3 /dev/loop4 /dev/loop5 /dev/loop6 /dev/loop7

[root@centos ~]#mknod /dev/loop8 b 7 8
[root@centos ~]#ls /dev/loop*
/dev/loop0 /dev/loop2 /dev/loop4 /dev/loop6 /dev/loop8
/dev/loop1 /dev/loop3 /dev/loop5 /dev/loop7
[root@centos ~]#cp p1 p2
[root@centos ~]#blkid p1 p2
p1: UUID=”7871347f-da18-4f67-9759-503c43a9cf76″ TYPE=”ext4″
p2: UUID=”7871347f-da18-4f67-9759-503c43a9cf76″ TYPE=”ext4″

[root@centos ~]#losetup /dev/loop8 p2
[root@centos ~]#mkdir /data/loop8; mount /dev/loop8 /data/loop8
[root@centos ~]#df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda2 50264772 5720948 41983824 12% /
tmpfs 502056 76 501980 1% /dev/shm
/dev/sda1 999320 34944 911948 4% /boot
/dev/sda3 30106576 99968 28470608 1% /data
/dev/sr0 3878870 3878870 0 100% /media/CentOS_6.9_Final
/dev/sdb1 1010780 1304 956464 1% /data/sdb1
/dev/sdb2 2005880 3096 1897560 1% /data/sdb2
/root/p1 95054 1551 88383 2% /data/mm
/dev/loop8 95054 1551 88383 2% /data/loop8
[root@centos ~]#ls /data/loop8
f1 lost+found

[root@centos ~]#vim /boot/grub/grub.conf 從新啟動生效

default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS 6 (2.6.32-696.el6.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.32-696.el6.x86_64 ro root=UUID=408b65d7-7551-480b-8916-5eff4cca1b00 rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet max_loop=100 使loop自動生成100個
initrd /initramfs-2.6.32-696.el6.x86_64.img

平時使用mount掛載，是在內存中掛載，exit不會丟失，重啟會丟失

掛載點和/etc/fstab
配置文件系統體系
被mount、fsck和其它程序使用
系統重啟時保留文件系統體系
可以在設備欄使用文件系統卷標
使用mount -a 命令掛載/etc/fstab中的所有文件系統

修改配置文件使啟動后自動掛載
[root@centos ~]#vim /etc/fstab
UUID=49002741-38ea-4585-9ef9-3f85cb99ae2c /data/sdb2 ext4 acl,nosuid 0 3
uuid 掛載點 文件類型 默認權限 幾天備份（需要配合備份命令） 啟動時按順序檢查文件完整性
mount -a 不用重啟直接生效

在配置文件中新加入的項可以用mount -a，已經生效的項想要修改不能直接使用mount -a
可以先卸載掛載然后在mount -a 或者 mount -o remount /data/sdb2

[root@centos ~]#tune2fs -U `uuidgen` /dev/sdb2 修改uuid，沒有寫入配置文件中，重啟
tune2fs 1.41.12 (17-May-2010)
系統無法正常啟動
輸入root口令
vim /etc/fatab 發現是只讀模式。
mount -o remount，rw / 將/重新掛載為rw模式
vim /etc/fatab 將錯誤行的最后一項3改成0.
重新啟動
已經可以啟動
連接xshell修改配置文件，改成正確的uuid，mount -a

想把/home分到一個獨立的分區上
1.備份
2.找一個大的硬盤分區，這個分區的大小要提前規劃好，一點分區完成無法修改
fdisk /dev/sdc
3.創建文件系統
mkfs.ext4 /dev/sdc1 -L /home
4.臨時創建一個文件夾，將/dev/sdc1掛載上去
mkdir /mnt/home ；mount /dev/sdc1 /mnt/home
5.發通知告知所有用戶不要登錄，切換到單用戶模式init 1
6.cp -a /home/* /mnt/home/中 確保所有文件都已經復制完成
7.rm -rf /home/*
8.vim /etc/fstab 添加/dev/sdc1的uuid 卷標，文件系統 默認項 0 0
9.mount -a
10.init 5
11.umount /mnt/home
12.rm -rf /mnt/home
根目錄無法遷移到別的硬盤以為根一直在被訪問

文件掛載配置文件
/etc/fstab每行定義一個要掛載的文件系統
要掛載的設備或偽文件系統
設備文件
LABEL：LABEL=””
UUID：UUID=””
偽文件系統名稱：proc, sysfs
掛載點
文件系統類型
掛載選項：defaults
轉儲頻率：0：不做備份 1：每天轉儲 2：每隔一天轉儲
自檢次序： 0：不自檢
1：首先自檢；一般只有rootfs才用1

特殊掛載關系
1.用文件當分區用 /root/p1 /mnt/p1 ext4 loop 0 0
2.掛載光胖 /dev/sr0 /mnt/cdrom iso9660 0 0
文件夾掛載文件夾 /boot /mnt/boot none bind 0 0

掛載交換分區
啟用：swapon
swapon [OPTION]… [DEVICE]
-a：激活所有的交換分區
-p PRIORITY：指定優先級
/etc/fstab:pri=value
禁用：swapoff [OPTION]… [DEVICE]

SWAP的優先級
可以指定swap分區0到32767的優先級，值越大優先級越高
如果用戶沒有指定，那么核心會自動給swap指定一個優先級，這個優先級從
-1開始，每加入一個新的沒有用戶指定優先級的swap，會給這個優先級減一
先添加的swap的缺省優先級比較高，除非用戶自己指定一個優先級，而用戶
指定的優先級(是正數)永遠高于核心缺省指定的優先級(是負數)
優化性能：分布存放，高性能磁盤存放

free -m 查看內存和swap

root@centos ~]#free -m
total used free shared buffers cached
Mem: 980 338 641 2 8 44
-/+ buffers/cache: 285 694
Swap: 2047 0 2047

讓swap使用一下 dd if=/dev/zero of=/dev/null bs=1024M count=1
現在新加入一個內存條，使內存變成2G，這是swap需要變成4G
想使swap變成4個G有兩個方法
1.刪除原來的swap在分化成4個G，但是如果swap正在被使用會使數據丟失
2.在添加一個2個G得swap，這個swap最好用一個快速的磁盤，或者用機械磁盤的外圈

[root@centos ~]#free -h
total used free shared buffers cached
Mem: 2.0G 361M 1.6G 2.4M 8.5M 53M
-/+ buffers/cache: 300M 1.7G
Swap: 2.0G 0B 2.0G

[root@centos ~]#fdisk /dev/sdc

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): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-10443, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-10443, default 10443): +2G

Command (m for help): t
Selected partition 1
Hex code (type L to list codes): 82
Changed system type of partition 1 to 82 (Linux swap / Solaris)

Command (m for help): p

Disk /dev/sdc: 85.9 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 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: 0xe72db920

Device Boot Start End Blocks Id System
/dev/sdc1 1 262 2104483+ 82 Linux swap / Solaris

[root@centos ~]#mkswap /dev/sdc1 -L swap_sdc1
Setting up swapspace version 1, size = 2104476 KiB
LABEL=swap_sdc1, UUID=ca1c9c9d-7ed6-45b3-89a4-e8ff36548d0b

[root@centos ~]#vim /etc/fstab

UUID=ca1c9c9d-7ed6-45b3-89a4-e8ff36548d0b swap swap defaults 0 0

[root@centos ~]#swapon -a

[root@centos ~]#free -h
total used free shared buffers cached
Mem: 2.0G 385M 1.6G 2.4M 9.2M 56M
-/+ buffers/cache: 319M 1.6G
Swap: 4.0G 0B 4.0G

[root@centos ~]#swapon -s 查看swap 優先級 數字越大優先越高
Filename Type Size Used Priority
/dev/sda5 partition 2097148 0 -1
/dev/sdc1 partition 2104476 0 -2

修改swap的優先級
[root@centos ~]#vim /etc/fstab

UUID=ca1c9c9d-7ed6-45b3-89a4-e8ff36548d0b swap swap defaults,pri=100 0 0

[root@centos ~]#swapon -s
Filename Type Size Used Priority
/dev/sda5 partition 2097148 0 -1
/dev/sdc1 partition 2104476 0 -2
[root@centos ~]#swapoff /dev/sdc1
[root@centos ~]#swapon -a
[root@centos ~]#swapon -s
Filename Type Size Used Priority
/dev/sda5 partition 2097148 0 -1
/dev/sdc1 partition 2104476 0 100

用文件做swap用
dd if=/dev/zero of=/swapfile bs=1024M count=2

mkswap /swapfile

vim /etc/fstab
/swapfile swap swap defaults 0 0

swapon -a

查看swap
swapon -s =cat /proc/swaps

刪除swap
swapoff /dev/sdc1
swapoff /swapfile
刪除vim /etc/fstab中相應的行
rm -rf /swapfile
fdisk /dev/sdc
d
1
w

使用光盤
在圖形環境下自動啟動掛載/run/media/<user>/<label>
否則就必須被手工掛載
mount /dev/cdrom /mnt/
eject命令卸載或彈出磁盤 彈入eject -t
創建ISO文件
cp /dev/cdrom /root/centos7.iso
mkisofs -r -o /root/etc.iso /etc
刻錄光盤
wodim –v –eject centos.iso

cp /dev/cdrom /root/centos7.iso制作一個ios文件
dd if=/dev/sr0 of=/root/centos7.iso

也可以將文件夾制作成iso文件

mkisofs -r -o etc.ios /etc/

掛載USB介質
查看USB設備是否識別
lsusb
被內核探測為SCSI設備
/dev/sdaX、/dev/sdbX、或類似的設備文件
在圖形環境中自動掛載
圖標在[計算機]窗口中創建
掛載在/run/media/<user>/<label>
手動掛載
mount /dev/sdb1 /mnt

tail -f /var/log/messages插入U盤時跟中
掛載U盤的時候 往U盤中傳輸文件需要多敲幾次 ，防止數據放在buffs中沒有傳過去
sync；sync；sync

常見工具
文件系統空間占用等信息的查看工具：
df [OPTION]… [FILE]…
-H 以1000為單位
-T 文件系統類型
-h: human-readable
-i：inodes instead of blocks
-P: 以Posix兼容的格式輸出 當設備名過長時自動對齊
查看某目錄總體空間占用狀態：
du [OPTION]… DIR
-h: human-readable
-s: summary –max-depth

[root@centos ~]#du -sh /*
27M /app
7.7M /bin
33M /boot
54M /data
704K /dev
42M /etc
672K /home
209M /lib
28M /lib64
16K /lost+found
5.8G /media
0 /misc
4.0K /mnt
0 /net
8.0K /opt
du: cannot access `/proc/4149/task/4149/fd/4′: No such file or directory
du: cannot access `/proc/4149/task/4149/fdinfo/4′: No such file or directory
du: cannot access `/proc/4149/fd/4′: No such file or directory
du: cannot access `/proc/4149/fdinfo/4′: No such file or directory
0 /proc
286M /root
17M /sbin
0 /selinux
4.0K /srv
0 /sys
1.4M /tmp
4.1G /usr
823M /var

[root@centos ~]#du -h –max-depth 0 /etc
42M /etc

工具dd
dd命令：convert and copy a file
用法：
dd if=/PATH/FROM/SRC of=/PATH/TO/DEST
bs=#：block size, 復制單元大小
count=#：復制多少個bs
of=file 寫到所命名的文件而不是到標準輸出
if=file 從所命名文件讀取而不是從標準輸入
bs=size 指定塊大小（既是是ibs也是obs)
ibs=size 一次讀size個byte
obs=size 一次寫size個byte
cbs=size 一次轉化size個byte
skip=blocks 從開頭忽略blocks個ibs大小的塊
seek=blocks 從開頭忽略blocks個obs大小的塊
count=n 只拷貝n個記錄

工具dd
conv=conversion[,conversion…] 用指定的參數轉換文件
轉換參數:
ascii 轉換 EBCDIC 為 ASCII
ebcdic 轉換 ASCII 為 EBCDIC
lcase 把大寫字符轉換為小寫字符
ucase 把小寫字符轉換為大寫字符
nocreat 不創建輸出文件
noerror 出錯時不停止
notrunc 不截短輸出文件
sync 把每個輸入塊填充到ibs個字節，不足部分用空(NUL)字
符補齊

[root@centos data]#cat f2
abcdefgh

[root@centos data]#dd if=f1 of=f2
0+1 records in
0+1 records out
7 bytes (7 B) copied, 0.000258348 s, 27.1 kB/s
[root@centos data]#cat f2 截斷模式，后面的統統干掉
123456
設備文件不截斷

[root@centos data]#dd if=f1 of=f2 bs=1 count=2 skip=3 seek=4 conv=notrunc
2+0 records in
2+0 records out
2 bytes (2 B) copied, 0.000281923 s, 7.1 kB/s
[root@centos data]#cat f2
abcd45gh

[root@centos data]#dd if=f2 of=f3 conv=ucase
0+1 records in
0+1 records out
9 bytes (9 B) copied, 0.000288186 s, 31.2 kB/s
[root@centos data]#cat f3
ABCD45GH

工具dd
備份MBR：
dd if=/dev/sda of=/tmp/mbr.bak bs=512 count=1
破壞MBR中的bootloader：
dd if=/dev/zero of=/dev/sda bs=64 count=1 seek=446
有一個大與2K的二進制文件fileA?，F在想從第64個字節位置開始讀取，需要讀
取的大小是128Byts。又有fileB, 想把上面讀取到的128Bytes寫到第32個字節開
始的位置，替換128Bytes，實現如下：
dd if=fileA of=fileB bs=1 count=128 skip=63 seek=31 conv=notrunc

工具dd
備份：
dd if=/dev/sdx of=/dev/sdy sdy硬盤一定比sdx大
將本地的/dev/sdx整盤備份到/dev/sdy
dd if=/dev/sdx of=/path/to/image
將/dev/sdx全盤數據備份到指定路徑的image文件
dd if=/dev/sdx | gzip >/path/to/image.gz
備份/dev/sdx全盤數據，并利用gzip壓縮，保存到指定路徑
恢復：
dd if=/path/to/image of=/dev/sdx
將備份文件恢復到指定盤
gzip -dc /path/to/image.gz | dd of=/dev/sdx
將壓縮的備份文件恢復到指定盤

工具dd
拷貝內存資料到硬盤
dd if=/dev/mem of=/root/mem.bin bs=1024
將內存里的數據拷貝到root目錄下的mem.bin文件
從光盤拷貝iso鏡像
dd if=/dev/cdrom of=/root/cd.iso
拷貝光盤數據到root文件夾下，并保存為cd.iso文件
銷毀磁盤數據
dd if=/dev/urandom of=/dev/sda1
利用隨機的數據填充硬盤，在某些必要的場合可以用來銷毀數據，執行此操作以后，
/dev/sda1將無法掛載，創建和拷貝操作無法執行

工具dd
得到最恰當的block size
dd if=/dev/zero bs=1024 count=1000000 of=/root/1Gb.file
dd if=/dev/zero bs=2048 count=500000 of=/root/1Gb.file
dd if=/dev/zero bs=4096 count=250000 of=/root/1Gb.file
通過比較dd指令輸出中命令的執行時間，即可確定系統最佳的block size大小

[root@CENTOS7 ~]#dd if=/dev/zero of=f1 bs=1024 count=1024000
1024000+0 records in
1024000+0 records out
1048576000 bytes (1.0 GB) copied, 27.7282 s, 37.8 MB/s
[root@CENTOS7 ~]#dd if=/dev/zero of=f1 bs=2048 count=512000
512000+0 records in
512000+0 records out
1048576000 bytes (1.0 GB) copied, 28.0448 s, 37.4 MB/s
[root@CENTOS7 ~]#dd if=/dev/zero of=f1 bs=4k count=256000
256000+0 records in
256000+0 records out
1048576000 bytes (1.0 GB) copied, 14.9327 s, 70.2 MB/s

工具dd
修復硬盤
dd if=/dev/sda of=/dev/sda
當硬盤較長時間（比如1,2年）放置不使用后，磁盤上會產生消磁點。當磁頭讀
到這些區域時會遇到困難，并可能導致I/O錯誤。當這種情況影響到硬盤的第一
個扇區時，可能導致硬盤報廢。上邊的命令有可能使這些數據起死回生,且這個
過程是安全高效的

什么是RAID
RAID:Redundant Arrays of Inexpensive（Independent） Disks
1988年由加利福尼亞大學伯克利分校（University of California-
Berkeley） “A Case for Redundant Arrays of Inexpensive Disks”
多個磁盤合成一個“陣列”來提供更好的性能、冗余，或者兩者都提供

RAID
提高IO能力
磁盤并行讀寫
提高耐用性
磁盤冗余來實現
級別：多塊磁盤組織在一起的工作方式有所不同
RAID實現的方式：
外接式磁盤陣列：通過擴展卡提供適配能力
內接式RAID：主板集成RAID控制器
安裝OS前在BIOS里配置
軟件RAID：通過OS實現

RAID級別
RAID-0:
讀、寫性能提升；
可用空間：N*min(S1,S2,…)
無容錯能力
最少磁盤數：2, 2+

RAID0又叫條帶集 假設有3塊硬盤，已3塊硬盤中最小的一個為準假設是100G，那么通過raid0就組成了一個300G的大硬盤，然后對這個300G的硬盤分區創建文件系統。
掛載。在掛載文件夾中創建一個100M的文件，將100M的文件分解成chunk，chunk的大小可以指定
假設是256k。
存儲時是1 2 3
4 5 6
……
讀寫速度快，但是沒有冗余，一但有一塊硬盤壞了，數據就被破壞了

RAID4 最少3塊硬盤才能實現
假設有3塊硬盤，已3塊硬盤中最小的一個為準假設是100G，那么通過raid0就組成了一個300G的大硬盤，然后對這個300G的硬盤分區創建文件系統。
掛載。在掛載文件夾中創建一個100M的文件，將100M的文件分解成chunk，chunk的大小可以指定
假設是256k。
存儲時是1 2 x x是校驗位，x1^2
3 4 x
…….
讀寫速度變快，一但有一塊硬盤壞了，可以繼續工作，但是由于校驗位運算太頻繁導致經常損壞

RAID5 最少3塊硬盤才能實現

假設有3塊硬盤，已3塊硬盤中最小的一個為準假設是100G，那么通過raid0就組成了一個300G的大硬盤，然后對這個300G的硬盤分區創建文件系統。
掛載。在掛載文件夾中創建一個100M的文件，將100M的文件分解成chunk，chunk的大小可以指定
假設是256k。
存儲時是1 2 3 x x是校驗位，x1^2^3
4 5 x 6
7 x 8 9
x 10 11 12
………….
讀寫速度變快，一但有一塊硬盤壞了，可以繼續工作,一但有一塊硬盤壞了，會導致服務器負載急劇增大，可能導致系統崩潰
所以一但有硬盤壞了要迅速更換.有一塊備用硬盤（spare disk）平時監視raid，一但有硬盤損壞則自己替換。

RAID6 最少4塊硬盤才能實現

假設有3塊硬盤，已3塊硬盤中最小的一個為準假設是100G，那么通過raid0就組成了一個300G的大硬盤，然后對這個300G的硬盤分區創建文件系統。
掛載。在掛載文件夾中創建一個100M的文件，將100M的文件分解成chunk，chunk的大小可以指定
假設是256k。

存儲時是1 2 x x x是校驗位，
3 x x 4 x的算法a+b=c
x x 5 6 na+mb=d
x 7 8 x

RAID-1：
讀性能提升、寫性能略有下降；
可用空間：1*min(S1,S2,…)
有冗余能力
最少磁盤數：2, 2N

就是兩兩互為鏡像. 一但刪除文件無法恢復

RAID級別
JBOD：Just a Bunch Of Disks
功能：將多塊磁盤的空間合并一個大的連續空間使用
可用空間：sum(S1,S2,…)
就是把幾塊硬盤組合在一起當一個大的硬盤使用，假設 1 2 3個
硬盤，1存滿在存2.

硬raid組合的硬盤在linux中只能看到一塊sda，別的看不到
軟raid可以看到有幾塊硬盤生成的設備名通常為/dev/md#

RAID級別
RAID7
可以理解為一個獨立存儲計算機，自身帶有操作系統和管理工具，可以獨立
運行，理論上性能最高的RAID模式
常用級別：
RAID-0, RAID-1, RAID-5, RAID-10, RAID-50, JBOD

軟RAID
mdadm：為軟RAID提供管理界面
為空余磁盤添加冗余
結合內核中的md(multi devices)
RAID設備可命名為/dev/md0、/dev/md1、/dev/md2、/dev/md3等
系統默認沒有raid