Centos7笔记 | 硬盘、Parted 分区、mount命令、Swap分区的扩展、、文件系统详解、

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发布于 2019-08-21 17:31:17

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发布于 2019-08-21 17:31:17

硬盘设备是由大量的扇区组成，每个扇区容量512字节，第一扇区最为重要，保存主引导记录和分区表信息。分别是主引导记录占用446，分区表占用64字节，结束符2字节，其中分区表中每记录一个信息占用16字节，最多只有四个分区，为了解决分区数不够，衍生出扩展分区。扩展分区可以用来创建逻辑分区，逻辑分区最多128个。

硬件设备	文件名称
IDE设备	/dev/hd[a-d]
SCSI/SATA/U盘/SAS	/dev/sd[a-p]
软驱	/dev/fd[0-1]
打印机	/dev/lp[0-15]
光驱	/dev/cdrom
鼠标	/dev/mouse
磁带机	/dev/st0或/dev/ht0

IDE硬盘接口在Linux中设备名为/dev/hda，SAS、SCSI、SATA硬盘接口在Linux中设备名为sda，高效云盘硬盘接口会识别为/dev/vda等。

硬盘的最小存储单位叫做Sector（扇区），每个Sector储存512字节。操作系统在读取硬盘的时候，不会逐个Sector的去读取，这样效率非常低，为了提升读取效率，操作系统会一次性连续读取多个Sector，即一次性读取多个Sector称为一个Block（块）。

由多个Sector组成的Block是文件存取的最小单位。Block的大小常见的有1KB、2KB、4KB，Block在Linux中常设置为4KB，即连续八个Sector组成一个Block。

硬盘分区分别分成（superblock）、inode、block，

Superblock：文件系统的整体信息，包含inode值和block块的使用的大小、剩余大小，相关的格式及信息。（记录inode和block的对应关系）

Inode：记录文件的属性和信息，同时会把文件的存储的位置生成一个编号（inode值：记录数据的存储位置（block在分区中所在位置））

Block块是存储文件的内容。因为每个 inode 与 block 都有编号，而每个文件都会占用一个 inode ，inode 内则有文件数据放置的 block 号码。如果能够找到文件的 inode，就可以找到该文件所放置数据的block号码，从而读取该文件内容。

1.1 Parted 分区

Parted 分区格式：gpt

1）将硬盘所有内容分到一个分区

将2.4T 硬盘分区操作

-1 参数：代表剩下的所有空间。

Parted工具中的mklabel 和mkpart 参数

1.2 mount命令实例

Mount常用案例演示如下：

mount  /dev/sdb1  /data 挂载/dev/sdb1分区至/data/目录

mount /dev/cdrom   /mnt 挂载Cdrom光盘至/mnt目录；

mount -t ntfs-3g /dev/sdc /data1 挂载/dev/sdc移动硬盘至/data1目录；

mount -o remount,rw /  重新以读写模式挂载/系统；

mount -t iso9660 -o loop centos7.iso /mnt 将centos7.iso镜像文件挂载至/mnt目录；

mount -t fat32 /dev/sdd1 /mnt  将U盘/dev/sdd1挂载至/mnt/目录；

mount -t nfs 192.168.1.11:/data/ /mnt  将远程192.168.1.11:/data目录挂载至本地/mnt目录。

1.3 文件系统详解

EXT4是第四代扩展文件系统（Fourth EXtended filesystem，EXT4）是Linux系统下的日志文件系统，是EXT3文件系统的后继版本；
EXT3类型文件系统支持最大16TB文件系统和最大2TB文件；
EXT4分别支持1EB（1EB=1024PB，1PB=1024TB）的文件系统，以及16TB的单个文件；
EXT3只支持32,000个子目录，而EXT4支持无限数量的子目录；
EXT4磁盘结构的inode个数支持40亿，而且EXT4的单个文件大小支持到16T(4K block size) ；
XFS是一个64位文件系统，最大支持8EB减1字节的单个文件系统，实际部署时取决于宿主操作系统的最大块限制，常用语64位操作系统，发挥更好的性能；
XFS一种高性能的日志文件系统，最早于1993年，由Silicon Graphics为他们的IRIX操作系统而开发，是IRIX 5.3版的默认文件系统；

1.4 Swap分区的扩展

dd 命令创建一个空文件，if指定一个来源/dev/zero（/dev/zero文件提供源源不断的“0”数据），of指定存储文件，bs=定义块的大小，count=定义块的数量

[root@localhost ~]# dd if=/dev/zero of=/root/test bs=100M count=20
20+0 records in
20+0 records out
2097152000 bytes (2.1 GB) copied, 42.9902 s, 48.8 MB/s
 [root@localhost ~]# mkswap  /root/test
Setting up swapspace version 1, size = 2047996 KiB
no label, UUID=13db4d1a-eb96-49fc-8e29-33e51c660ea5
 [root@localhost ~]# free -hm
        total    used     free    shared  buff/cache   available
Mem:     976M    113M     170M    6.7M      692M        686M
Swap:    2.0G     0B       2.0G
[root@localhost ~]# swapon /root/test
swapon: /root/test: insecure permissions 0644, 0600 suggested.
[root@localhost ~]# free -hm
       total        used        free      shared  buff/cache   available
Mem:    976M        115M        168M        6.7M        692M        684M
Swap:   4.0G          0B        4.0G
[root@localhost ~]#
[root@localhost ~]# swapoff  /root/test
[root@localhost ~]#
[root@localhost ~]# free -m
        total    used     free   shared  buff/cache   available
Mem:     976      114      168      6      693         685
Swap:    2047     0        2047

1.5 使用xfs文件系统superblock实验

1. 创建一个XFS文件系统

[root@localhost ~]# mkfs.xfs -f /dev/sdb1meta-data=/dev/sdb1              
[root@localhost ~]# cat /etc/fstab |grep sdsb1/dev/sdb1 /test xfs defaults 0 0
[root@localhost ~]# mount -a[root@localhost ~]# df -h
/dev/sdb1                         30G  610M   30G   2% /test

2. 卸载文件系统/test, 并且破坏superblock

[root@localhost ~]# umount /test
[root@localhost ~]# dd if=/dev/zero of=/dev/sdb1 bs=512 count=1
1+0 records in
1+0 records out512 bytes (512 B) copied, 0.00251096 s, 204 kB/s

3. 再次挂载报错

[root@localhost ~]# mount -a
mount: wrong fs type, bad option, bad superblock on /dev/sdb1,       
            missing codepage or helper program, or other error       
            In some cases useful info is found in syslog - try       
        dmesg | tail  or so


[root@localhost ~]# dmesg
[22597379.623449] XFS (sdb1): bad magic number[22597379.624372] XFS (sdb1): SB validate failed

4. 恢复superblock

[root@localhost ~]# xfs_repair /dev/sdb1
Phase 1 - find and verify superblock...bad primary superblock - 
bad magic number !!!


attempting to find secondary superblock......
......found candidate secondary superblock...
verified secondary superblock...
writing modified primary superblock
sb realtime bitmap inode 18446744073709551615 (NULLFSINO) 
inconsistent with calculated value 129
resetting superblock realtime bitmap ino pointer to 129
sb realtime summary inode 18446744073709551615 (NULLFSINO) 
inconsistent with calculated value 130
resetting superblock realtime summary ino pointer to 130
Phase 2 - using internal log       
      - zero log...        
     - scan filesystem freespace and inode maps...
sb_icount 0, counted 64
sb_ifree 0, counted 60
sb_fdblocks 7860552, counted 7712768       
    - found root inode chunkPhase 3 - for each AG...       
     - scan and clear agi unlinked lists...        
    - process known inodes and perform inode discovery...       
    - agno = 0        
    - agno = 1        
    - agno = 2        
    - agno = 3        
    - process newly discovered inodes...
Phase 4 - check for duplicate blocks...        
    - setting up duplicate extent list...        
    - check for inodes claiming duplicate blocks...        
    - agno = 0        
    - agno = 1        
    - agno = 2        
    - agno = 3
Phase 5 - rebuild AG headers and trees...        
    - reset superblock...Phase 6 - check inode connectivity...       
     - resetting contents of realtime bitmap and summary inodes       
    - traversing filesystem ...        
    - traversal finished ...        
    - moving disconnected inodes to lost+found ...
Phase 7 - verify and correct link counts...
Note - stripe unit (0) and width (0) fields have been reset.
Please set with mount -o sunit=<value>,swidth=<value>done

5. 确认是否已经恢复

[root@localhost ~]# mount -a
[root@localhost ~]# df -h
/dev/sdb1                        30G  610M   30G   2% /test

1.2 修复ext4分区superblock 问题

[root@localhost ~]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/centos-root   17G  1.7G   16G  10% /
devtmpfs                 478M     0  478M   0% /dev
tmpfs                    489M     0  489M   0% /dev/shm
tmpfs                    489M  6.7M  482M   2% /run
tmpfs                    489M     0  489M   0% /sys/fs/cgroup
/dev/sda1               1014M  127M  888M  13% /boot
tmpfs                     98M     0   98M   0% /run/user/0
/dev/sdb                  20G   33M   20G   1% /test
/dev/sdc1                 20G   44M   19G   1% /test1


[root@localhost ~]# umount /test1
[root@localhost ~]# !dd
dd if=/dev/zero of=/dev/sdc1  bs=100M count=10
10+0 records in
10+0 records out
1048576000 bytes (1.0 GB) copied, 1.72432 s, 608 MB/s

 [root@localhost ~]# mount -a
mount: wrong fs type, bad option, bad superblock on /dev/sdc1,
       missing codepage or helper program, or other error
 
       In some cases useful info is found in syslog - try
       dmesg | tail or so.

 [root@localhost ~]# fsck -t ext4 /dev/sdc1
fsck from util-linux 2.23.2
e2fsck 1.42.9 (28-Dec-2013)
ext2fs_open2: Bad magic number in super-block
fsck.ext4: Superblock invalid, trying backup blocks...
fsck.ext4: Bad magic number in super-block while trying to open /dev/sdc1
 
The superblock could not be read or does not describe a correct ext2
filesystem.  If the device is valid and it really contains an ext2
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>

[root@localhost ~]# mke2fs  -S /dev/sdc1
-S 仅写入superblock与group descriptors
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
1310720 inodes, 5242631 blocks
262131 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
160 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000
 
Allocating group tables: done                            
Writing superblocks and filesystem accounting information: done

[root@localhost ~]# mount /dev/sdc1
mount: mount /dev/sdc1 on /test1 failed: Stale file handle
[root@localhost ~]#
[root@localhost ~]# fsck -t ext4 -y /dev/sdc1

检查特定类型的文件系统（ext4），-y检测完成之后并自动修复

fsck from util-linux 2.23.2
e2fsck 1.42.9 (28-Dec-2013)
/dev/sdc1 contains a file system with errors, 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? ye
/lost+found not found.  Create? yes
Pass 4: Checking reference counts
Pass 5: Checking group summary information
Block bitmap differences:  +(0--1539) +(32768--34306) +(65536--66049) +(98304--99842) +(131072--131585) +(163840--165378) +(196608--197121) +(229376--230914)
Fix? yes
Free blocks count wrong for group #0 (31227, counted=31226).
Fix? yes
Free blocks count wrong (5149114, counted=5149113).
Fix? yes
Inode bitmap differences:  +1 +(3--10)
Fix? yes
Free inodes count wrong for group #0 (8191, counted=8181).
Fix? yes
Directories count wrong for group #0 (1, counted=2).
Fix? yes
Free inodes count wrong (1310719, counted=1310709).
Fix? yes
/dev/sdc1: ***** FILE SYSTEM WAS MODIFIED *****
/dev/sdc1: 11/1310720 files (0.0% non-contiguous), 93518/5242631 block
[root@localhost ~]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/centos-root   17G  1.7G   16G  10% /
devtmpfs                 478M     0  478M   0% /dev
tmpfs                    489M     0  489M   0% /dev/shm
tmpfs                    489M  6.7M  482M   2% /run
tmpfs                    489M     0  489M   0% /sys/fs/cgroup
/dev/sda1               1014M  127M  888M  13% /boot
tmpfs                     98M     0   98M   0% /run/user/0
/dev/sdb                  20G   33M   20G   1% /test
/dev/sdc1                 20G   44M   19G   1% /test1