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鸟哥的linux私房菜学习笔记《十七》设置开机挂载及构架swap

2017-03-07 16:29 471 查看

开机挂载/etc/fstab及/etc/mtab

共分了六列：

第一列：磁盘设备文件名或该设备的Lable

第二列：挂载点（mount point）

第三列：磁盘分区的文件系统

第四列：文件系统参数

第五列：能否被dump备份命令作用

第六列：是否已fsck检验扇区

在/etc/fstab新增一行：

特殊设备loop挂载（镜像文件不刻录就挂载使用）

[root@CentOS Desktop]# ll -h ubuntu-14.04.5-server-i386.iso
-rw-r--r--. 1 kevin kevin 595M Feb 26 03:26 ubuntu-14.04.5-server-i386.iso

[root@CentOS Desktop]# mkdir /mnt/centos_dvd

[root@CentOS Desktop]# mount -o loop ubuntu-14.04.5-server-i386.iso /mnt/centos_dvd/

[root@CentOS Desktop]# df
Filesystem                                         1K-blocks    Used Available Use% Mounted on
/dev/sda2                                           10321208 7488116   2308804  77% /
tmpfs                                                 515264     228    515036   1% /dev/shm
/dev/sda3                                           10321208 1025616   8771304  11% /home
/dev/sr0                                             3757116 3757116         0 100% /root
/home/kevin/Desktop/ubuntu-14.04.5-server-i386.iso    609280  609280         0 100% /mnt/centos_dvd

[root@CentOS Desktop]# ll /mnt/centos_dvd/
total 173
dr-xr-xr-x. 1 root root   2048 Aug  3  2016 boot
dr-xr-xr-x. 1 root root   2048 Aug  3  2016 dists
dr-xr-xr-x. 1 root root   2048 Aug  3  2016 doc
dr-xr-xr-x. 1 root root   2048 Aug  3  2016 install
dr-xr-xr-x. 1 root root  18432 Aug  3  <
115e7
span class="hljs-number">2016 isolinux
-r--r--r--. 1 root root 143592 Aug  3  2016 md5sum.txt
dr-xr-xr-x. 1 root root   2048 Aug  3  2016 pics
dr-xr-xr-x. 1 root root   2048 Aug  3  2016 pool
dr-xr-xr-x. 1 root root   2048 Aug  3  2016 preseed
-r--r--r--. 1 root root    235 Aug  3  2016 README.diskdefines
lr-xr-xr-x. 1 root root      1 Aug  3  2016 ubuntu -> .

[root@CentOS Desktop]# umount /mnt/centos_dvd

新建大文件以制作loop设备文件

1 . 准备

2 . 创建大型文件

# 创建一个空的文件在/home/loopdefv：

[root@CentOS Desktop]# dd if=/dev/zero of=/home/loopdev bs=1M count=512
512+0 records in
512+0 records out
536870912 bytes (537 MB) copied, 0.859372 s, 625 MB/s

# if是input file ，输入文件，那个/dev/zero是会一直输出0的设备

# of是output file，将一堆零写入到后面的文件中

# bs是每个block大小，就像文件系统那样的block

# count 则是总共几个bs的意思

[root@CentOS Desktop]# ll -h /home/loopdev
-rw-r--r--. 1 root root 512M Mar  7 03:53 /home/loopdev

3 . 格式化

# 很简单就创建一个512MB的文件，接下来当然是格式化了

[root@CentOS Desktop]# mkfs -t ext3 /home/loopdev
mke2fs 1.41.12 (17-May-2010)
/home/loopdev is not a block special device.
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
32768 inodes, 131072 blocks
6553 blocks (5.00%) reserved for the super user
...............
...............

4 . 挂载

# 利用-o loop参数

[root@CentOS Desktop]# mount -o loop /home/loopdev /media/cdrom
[root@CentOS Desktop]# df
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda2       10321208 7488124   2308796  77% /
tmpfs             515264     228    515036   1% /dev/shm
/dev/sda3       10321208 1549908   8247012  16% /home
/dev/sr0         3757116 3757116         0 100% /root
/home/loopdev     516040   16800    473028   4% /media/cdrom

内存交换空间的创建

1 . 使用物理分区构架swap

# 先进行分区：

[root@CentOS kevin]# fdisk /dev/sdc

# 新建分区：

Command (m for help): n
Command action
e   extended
p   primary partition (1-4)

# 选择主分区：

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): +256M

# 显示分区：

Command (m for help): p
................
................
Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1          34      273073+  83  Linux

# 更改分区系统ID（参数为t）

Command (m for help): t
Selected partition 1

# 按l会显示ID表：

Hex code (type L to list codes): l

0  Empty           24  NEC DOS         81  Minix / old Lin bf  Solaris
1  FAT12           39  Plan 9          82  Linux swap / So c1  DRDOS/sec (FAT-
2  XENIX root      3c  PartitionMagic  83  Linux           c4  DRDOS/sec (FAT-
3  XENIX usr       40  Venix 80286     84  OS/2 hidden C:  c6  DRDOS/sec (FAT-
4  FAT16 <32M      41  PPC PReP Boot   85  Linux extended  c7  Syrinx
5  Extended        42  SFS             86  NTFS volume set da  Non-FS data
6  FAT16           4d  QNX4.x          87  NTFS volume set db  CP/M / CTOS / .
7  HPFS/NTFS       4e  QNX4.x 2nd part 88  Linux plaintext de  Dell Utility
8  AIX             4f  QNX4.x 3rd part 8e  Linux LVM       df  BootIt
9  AIX bootable    50  OnTrack DM      93  Amoeba          e1  DOS access
a  OS/2 Boot Manag 51  OnTrack DM6 Aux 94  Amoeba BBT      e3  DOS R/O
b  W95 FAT32       52  CP/M            9f  BSD/OS          e4  SpeedStor
c  W95 FAT32 (LBA) 53  OnTrack DM6 Aux a0  IBM Thinkpad hi eb  BeOS fs
e  W95 FAT16 (LBA) 54  OnTrackDM6      a5  FreeBSD         ee  GPT
f  W95 Ext'd (LBA) 55  EZ-Drive        a6  OpenBSD         ef  EFI (FAT-12/16/
10  OPUS            56  Golden Bow      a7  NeXTSTEP        f0  Linux/PA-RISC b
11  Hidden FAT12    5c  Priam Edisk     a8  Darwin UFS      f1  SpeedStor
12  Compaq diagnost 61  SpeedStor       a9  NetBSD          f4  SpeedStor
14  Hidden FAT16 <3 63  GNU HURD or Sys ab  Darwin boot     f2  DOS secondary
16  Hidden FAT16    64  Novell Netware  af  HFS / HFS+      fb  VMware VMFS
17  Hidden HPFS/NTF 65  Novell Netware  b7  BSDI fs         fc  VMware VMKCORE
18  AST SmartSleep  70  DiskSecure Mult b8  BSDI swap       fd  Linux raid auto
1b  Hidden W95 FAT3 75  PC/IX           bb  Boot Wizard hid fe  LANstep
1c  Hidden W95 FAT3 80  Old Minix       be  Solaris boot    ff  BBT
1e  Hidden W95 FAT1

# swap分区为82号：

Hex code (type L to list codes): 82

# 显示分区情况：

Command (m for help): p
Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1          34      273073+  82  Linux swap / Solaris

# 保存修改：

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

Calling ioctl() to re-read partition table.
Syncing disks.

# 这个很重要，让内更新分区表：

[root@CentOS kevin]# partprobe
Warning: WARNING: the kernel failed to re-read the partition table on /dev/sda (Device or resource busy).  As a result, it may not reflect all of your changes until after reboot.
Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.
Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.
Error: Invalid partition table - recursive partition on /dev/sr0.
[root@CentOS kevin]#

文件系统格式ID对照表：

# 开始构建swap分区：

[root@CentOS kevin]# mkswap /dev/sdc1
Setting up swapspace version 1, size = 273068 KiB
no label, UUID=1ff052d0-25bb-4b2d-abf7-3014ad003afd

# 非常快速

# 开始查看与加载：

[root@CentOS kevin]# free
total       used       free     shared    buffers     cached
Mem:       1030528     268428     762100          0      33188     120352
-/+ buffers/cache:     114888     915640
Swap:      1048568          0    1048568

# 查看物理内存，总共-已用-剩余-共享-缓冲-快取

[root@CentOS kevin]# swapon /dev/sdc1

[root@CentOS kevin]# free
total       used       free     shared    buffers     cached
Mem:       1030528     268520     762008          0      33208     120364
-/+ buffers/cache:     114948     915580
Swap:      1321632          0    1321632

# 有增加了

[root@CentOS kevin]# swapon -s
Filename                Type        Size    Used    Priority
/dev/sda5                               partition   1048568 0   -1
/dev/sdc1                               partition   273064  0   -2

# 上面列出了使用的swap设备有哪些的意思

使用文件构建swap

# 使用dd命令新增一个128M的文件在/tmp下面：

[root@CentOS kevin]# dd if=/dev/zero of=/tmp/swap bs=1M count=128
128+0 records in
128+0 records out
134217728 bytes (134 MB) copied, 1.01558 s, 132 MB/s
[root@CentOS kevin]# ll -h /tmp/swap
-rw-r--r--. 1 root root 128M Mar  7 04:37 /tmp/swap

# 使用mkswap将/tmp/swap这个文件格式化为swap的文件格式：

[root@CentOS kevin]# mkswap  /tmp/swap
Setting up swapspace version 1, size = 131068 KiB
no label, UUID=a3af4d82-bd1c-490f-a02e-125806aa82e8

# 这个命令使用时要特别注意，因为弄错字节会使系统挂掉

# 使用swapon来将/tmp/swap启动：

[root@CentOS kevin]# free
total       used       free     shared    buffers     cached
Mem:       1030528     402576     627952          0      33744     251648
-/+ buffers/cache:     117184     913344
Swap:      1321632          0    1321632
[root@CentOS kevin]# swapon /tmp/swap
[root@CentOS kevin]# swapon -s
Filename                Type        Size    Used    Priority
/dev/sda5                               partition   1048568 0   -1
/dev/sdc1                               partition   273064  0   -2
/tmp/swap                               file        131064  0   -3

# 使用swapoff关掉swap file：

[root@CentOS kevin]# swapoff /tmp/swap
[root@CentOS kevin]# swapoff /dev/sdc1
[root@CentOS kevin]# free
total       used       free     shared    buffers     cached
Mem:       1030528     402396     628132          0      33764     251648
-/+ buffers/cache:     116984     913544
Swap:      1048568          0    1048568

swap使用上的限制