3) Check the hardware operating system
4) operating system infrastructure optimization
02. Course Knowledge Review
1) level file system operation
File path information: / etc / inittab
File Function Description: Define what software program the system to automatically turn on after starting
System run level: runlevel command to view the current level
centos6 (level) default level 3
0 -------------- level system shutdown level
1 ------------ system-level single-user system used to crack passwords root, (no network service mode) rescue response system data
2 ----------------- multi-user mode, no network service model
3 -------- multi-user mode with network service mode (system power-on default level)
4 ------------------ unused
5 ------------ graphical system level
6 ------------- restart level
Setting method:
Temporary settings: init level digital (switching level)
Permanent setting: vim / etc / inittab the above mentioned id: 3 : initdefault: --- default run level 3 messages appear ------ centos6
centos7 (target operating mode) default level 3
systemctl get-default view the current level
ll / usr / lib / systemd / system / runlevel * target level directory View
/usr/lib/systemd/system/runlevel0.target -> poweroff.target /usr/lib/systemd/system/runlevel1.target -> rescue.target /usr/lib/systemd/system/runlevel2.target -> multi-user.target /usr/lib/systemd/system/runlevel3.target -> multi-user.target /usr/lib/systemd/system/runlevel4.target -> multi-user.target /usr/lib/systemd/system/runlevel5.target -> graphical.target /usr/lib/systemd/system/runlevel6.target -> reboot.target
Setting method:
Temporary settings: init level digital
Permanently set:
vim /etc/inittab
Modify the default operating system level systemctl set-default multi-user.target
2) system login prompt:
File path information: / etc / motd
File Purpose: The system displays the login prompt
vi / etc / motd
xxxxxxxxxxxxxxxxxxxxxxx
File path information: / etc / issue / etc / issue / issue.net
File Purpose: display a message before you log on
vi /etc/issue /etc/ issue/issue.net
xxxxxxxxxxxxxxxxxx
2) the system host name of the configuration file (temporarily modify with immediate effect)
File path information: / etc / hostname
File Function Description: modify the host name
PS: business needs, statistical information == Asset Management host Host name of the host network address of the host computer brands and models host CPU host host memory to store information
Host Name Name (Planning): Regional (BJ) --- room name (mobile idc) ---- enclosure number (010203) --- Machine number (01)
Changing the system name:
Temporary: hostname oldboy disconnect reconnect after the change to take effect restart shutdown fail
Permanent: Method One: vim / etc / hostname reboot to take effect
Method Two: hostnamectl set-hostname oldboy both temporary and permanent changes take effect reconnection
04. System software installation method (/ usr directory of important files / usr / local | / opt --- third-party software installation directory)
Method 1: Use the rpm command to install the software (process: official website to download the software installation program --- rpm to install software)
Features (disadvantages) Description: the need to install software to address software dependencies
Command to use:
Prerequisite: must have software package
rpm -ivh package name
i --- install software
v --- shows the installation process
h ------ humanized visible
(For example
The download process wget https://mirrors.aliyun.com/centos/7.7.1908/os/x86_64/Packages/vim-enhanced-7.4.629-6.el7.x86_64.rpm installation rpm -ivh vim-enhanced-7.4 .629-6.el7.x86_64.rpm)
rpm: RPM package management command packages have become rpm package
Method 2: Using yum command to install the software 360 software housekeeping (yum warehouse)
Features: Download and install the software automatically resolve dependencies
Disadvantages: over-reliance on the network, you can not customize the functionality
Guide me: yum install -y software to confirm the name ------------- -y
yum reinstall -y Software Name (re-install or repair software)
The name must be some yum Curry
Method three: Install the software using the method to compile (source installation software)
Features: Flexible to install or configure software features
Disadvantages: can not resolve software dependencies installed high complexity operation and demonstration:
Trilogy (Configuration configure ---- compiler make ---- install make install)
Software program source code package -----> configure (specify the software installation directory specified software features) ---------> make compilation -------> make install installation
Method four: using the binary method to install the software package Features: Green software (used directly after decompression software) Database Service
Disadvantages: can not resolve software dependencies single function
Installation process:
Binary archive ------> decompression ---------> Save data better -----> simple configuration --------> Launcher
05. Check the system log file
Log File: Record system information or services running normal / abnormal information *
/ var directory of important documents:
1 / var / log / messages --- recording system or software operation (normal / abnormal) 2 / var / log / log Secure --- the information recording user
))> / Var / log / secure emptying file information
Dec 4 18:49:42 oldboy-test1 sshd[7961]: Accepted password for root from 10.0.0.1 port 49380 ssh2 01 02 03 04
01. login connection time information
02. Displays the host name information
03. What is login sshd (remote connection) login (local connection)
04. For more information logon process concerns the failure information
How to view the log information: cat
only view the latest information: Method a
head to view the file information --- 10 lines of information before the file
tail file information --- see the end of the file information 10 lines
before the head -n file view file information --- few lines
tail -n file information --- see the end of a few lines of a file
tail -f file information --- the latest changes in real-time view the log file data content
PS:
tail -f parameter and the -F parameter difference
tail -f when deleting files when, view real-time process will end
tail -F when a file is deleted, view real-time process will end, but if the file was created out of the same command again, will continue to track
two: focus on the specified error message Fail
grep "attention information" file
-C - B -A -i
06. The system of foundation:
1) optimization system users: How to Create a User password how to create a user how to delete a user
How to Create a User: (operating under the root user)
useradd user-oldgirl
Check to confirm whether the user has been created: id user-oldgirl
b How to set a password:
Method a: Interactive Set Password passwd user-oldgirl ----> password information entered twice
Method Two: Free interactive password echo 654321 | passwd --stdin user-oldgirl
How to use the new user:
Method One: Re-establish a new remote connection
Method two: su ----- switch user su - username
PS: Emperor root - without a password information - civilian oldboy civilian oldboy- require password information - Emperor root
c how to delete a user: (operating under the root user)
userdel user-girl
Download Optimization 2) system: yum install download
3) optimization of system security: security-related services shut down
PS: System security is inversely proportional system performance
Time 4) optimization of the system: the system synchronization area
5) character coding optimization: to solve the Chinese garbled message system becomes Chinese
6) Remote connection optimization: improve the speed remote connection