Linux Key Knowledge Summary

1th Chapterthe composition of the computer

CPU Hard Disk Memory power

2nd ChapterMemory

Memory is a temporary storage file, data loss after power outage

Program: Write data to disk

Process: Running program read in memory

Daemon: A program that has been running

3rd Chapterimprove the user experience

Large concurrency data is first written to the memory disk to be read on disk

Small users first put data into disk to read data from memory

4th Chapter Bufferand theCatchthe Difference

Buffer buffers write data into memory

The catch cache reads data from memory

Storage for permanent storage of data on disk

5th Chapterthe development process of computer

Egg-man-man-man

Unix born at Bell Labs

Tan Ningbong Studies the teaching of Minix teaching

Founder of the Stallman Free Software Foundation GNU Project

Tawas the father of Linux

The GNU kernel hasn't been developed yet. The core is bash gawk

GPL is a general public license that everyone is free to use freely and will be modified and distributed.

Chapter 6th SSHServer Connectivity Failure

First of all, see if the road ping 10.0.0.200 if you pass

See if anyone is robbing the firewall. Iptables (chkconfig iptables off)

Chkconfig |grep iptables (view)

See if anyone buys a ticket.

Does the SSH service turn on telnet10.0.0.200 22

7th Chaptermethods for server partitioning

Method One There's no important data.

/boot storage System is the boot information 200M

Swap partition to prevent memory when memory is greater than 8G give 8G if memory is less than 8G 1.5 times times of memory 768M

/How much is left

Method Two when there is important information

/boot boot System Information 200M

Swap partition prevents memory from running out when memory is greater than 8G to 8 g, memory is 1.5 times times 768M when memory is less than 8G

/root Partition 20-200g

/data Store important Information how much is left

Method Three I don't know if the data is heavy.

/boot boot System Information M

Swap partition prevents memory from running out when memory is greater than 8G to 8G if it is less than 8G time 1.5 times times of memory

/Root 20-200g

The remaining memory, left to the person to use

8th ChapterViewSshdwhether the service exists

[Email protected] oldboy]# ps-ef |grep sshd

Root 1533 1 0 13:34? 00:00:00/usr/sbin/sshd

Root 1627 1533 0 13:35? 00:00:01 sshd: [Email protected]/0

Root 1726 1631 0 14:13 pts/0 00:00:00 grep sshd

This will run the

ps-ef |grep sshd to see if the SSH service is running

Rpm-qa | grep SSH can see the system in the SSH installation package

RPM-QL openssh-3.5p1-6 View the installation package installation information (such as installation path, configuration file, etc.)

If it is not running, the

[Email protected] oldboy]#/etc/rc.d/init.d/sshdstart

[[Email protected] oldboy]# service sshd start

[Email protected] oldboy]# NETSTART-NTLP

If you're still not connected, try shutting down the firewall.

Service Iptables Stop

9th ChapterOptimizedSELinux

Temporarily closed

[Email protected] ~]# Setenforce

Usage:setenforce [Enforcing | Permissive | 1 | 0]

[Email protected] ~]# Setenforce 0

[Email protected] ~]# Getenforce

Permissive

Permanently closed

[Email protected] ~]# Vim/etc/selinux/config

Selinux=enforcing modified to Disabled

[[email protected] ~]# grep "=disabled"/etc/selinux/config

Selinux=disabled

Restart takes effect

10th Chaptershutting down the firewall

1. Temporarily closed

[[email protected] ~]#/etc/init.d/iptables start

iptables:applying firewall rules: [OK]

[Email protected] ~]#/etc/init.d/iptables status

Table:filter

Chain INPUT (Policy ACCEPT)

Num Target prot opt source destination

1 ACCEPT All – 0.0.0.0/0 0.0.0.0/0 State related,established

2 ACCEPT ICMP--0.0.0.0/0 0.0.0.0/0

3 ACCEPT All--0.0.0.0/0 0.0.0.0/0

4 ACCEPT TCP--0.0.0.0/0 0.0.0.0/0 State NEW tcpdpt:22

5 REJECT All--0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited

Chain FORWARD (Policy ACCEPT)

Num Target prot opt source destination

1 REJECT All--0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited

Chain OUTPUT (Policy ACCEPT)

Num Target prot opt source destination

[[email protected] ~]#/etc/init.d/iptables stop

Iptables:setting chains to Policy Accept:filter [OK]

iptables:flushing firewall rules: [OK]

iptables:unloading modules: [OK]

[Email protected] ~]#/etc/init.d/iptables status

Iptables:firewall is not running.

Permanently closed

[Email protected] ~]# chkconfig iptables off

[Email protected] ~]# chkconfig |grep iptables

Iptables 0:off 1:off 2:off 3:off 4:off5:off 6:off

run on top of 3

[[email protected] ~]# chkconfig--level 3 iptables on

[Email protected] ~]# chkconfig |grep iptables

Iptables 0:off 1:off 2:off 3:on 4:off5:off 6:off

11th Chapter Linuxthe RunLevel in

0 shutdown (not normally set)

1 Single-User mode

2 Multi-user mode without NFS (network configuration file)

3 full multi-user mode, Command mode (common in work)

4 Not used

5 Image Interface Mode

6 Restart (not normally set)

12th Chapter Linuxgarbled text

A typical Linux system uses a character set that differs from the Xshell software's character set. There will be garbled

Fix garbled

[Email protected] ~]# Export.utf8

[Email protected] ~]# echo $LANG

En_us.utf8

[Email protected] ~]# cat/etc/sysconfig/i18n

Lang= "en_US. UTF-8 "

Sysfont= "Latarcyrheb-sun16"

Lang= "en_US. UTF-8 "

13th Chapterrun-level modifications

Temporary:

[Email protected] ~]# RunLevel

N 3

[[Email protected] ~]# Init 5

[Email protected] ~]# RunLevel

3 5

[[Email protected] ~]# Init 3

[Email protected] ~]# RunLevel

5 3

It's resumed after a reboot.

2. Permanent Modification

[[email protected] ~]# grep "ID:"/etc/inittab

Id:3:initdefault:

14th ChapterSetting Aliases

1. view aliases with alias

Temporarily modify aliases

[[email protected] ~]# alias net= ' Cat/etc/sysconfig/network-scripts/ifcfg-eth0 '

[[email protected] ~]# net

Device=eth0

Hwaddr=00:0c:29:0e:80:e8

Type=ethernet

Uuid=6f54df19-76a0-4fd6-9e9a-462246fdcbea

Onboot=yes

Nm_controlled=yes

Bootproto=none

ipaddr=10.0.0.200

netmask=255.255.255.0

gateway=10.0.0.2

Userctl=no

Peerdns=yes

Ipv6init=no

dns1=223.5.5.5

dns2=223.6.6.6 not effective

1. Permanently modify aliases

[Email protected] ~]# cat/etc/profile

[[email protected] ~]# alias net= ' Cat/etc/sysconfig/network-scripts/ifcfg-eth0 '

[Email protected] ~]# source/etc/profile

[[email protected] ~]# alias

Alias cp= ' Cp-i '

Alias l.= ' ls-d. *--color=auto '

Alias ll= ' Ls-l--color=auto '

Alias ls= ' ls--color=auto '

Alias mv= ' Mv-i '

Alias net= ' Cat/etc/sysconfig/network-scripts/ifcfg-eth0 '

Alias rm= ' echo do not user RM command '

Alias Which= ' Alias | /usr/bin/which--tty-only--read-alias--show-dot--show-tilde ' effective

15th Chapter Linuxconfiguration file for the operating level of the system

/etc/inittable

0 Turn off the machine

1 Single-User mode

2 Multi-user mode

3 full multi-user mode command mode

4 Not used

5 Graphical interface mode

6 restart

16th Chapter LinuxBoot- up process

BIOS self-Test

MBR boot

Grub Menu

Load kernel

Run the INIT process first process

Select Run Level Etc/inittab

Initialize the system settings host name and IP address etc/rc.d/rc.sysinit

Self-starting software commands or scripts based on RunLevel

Mingetty Display Login Interface

17th ChapterNetworkPingcause of the failure to pass

Network does not pass

If Ping baidu.com does not pass

Ping the IP address of the outside network if the

That's the DNS configuration problem.

Cat >>/etc/sysconfig/network-scripts/ifcfg-eth0<<eof

dns1=223.5.5.5

dns2=223.6.6.6

Eof

Restart effective or/etc/init.d/network restart

18th Chapter Inodeand theBlock

1. How did it come about?

To create a file system formatted

2. What do you mean?

The inode is where the index node holds the file attributes and block

The block holds the actual data (the file name is stored in the block of the previous level directory)

3. Features

1) Create a non-empty file to occupy an inode and at least one block

2) If the inode of two files is the same, the two files are hard to connect to each other, the condition that the two files must be in the same partition

3) Block 4k, if the storage of small files 1k, the remaining space is wasted

4) inode 256 bytes

19th Chapterthe difference between hard links and soft links

There are two types of links in Linux, one is a soft link and the other is a hard link

1. How to create

LN creates a hard link with no arguments by default, Ln-s creates a soft link

2. Meaning

A hard-link file is the same as the inode number of the source file (in the same file system or partition), and the soft link is equivalent to a shortcut inside windows

3. Features:

You cannot create a hard link to a directory, but a soft link can,

Soft links can cross file systems, but hard links can not

4. Why not?

Delete soft link files, no impact on source files and hard links

Delete hard link files, no effect on source files and soft link files

Delete source files, no impact on hard-link files, but have impact on soft link files, will cause soft link failure

Also delete the soft and hard connection file, the entire file will be really deleted

Linux Key Knowledge Summary