1. Mainstream Databases
Currently, the mainstream databases used in software development process include Oracle, DB2, SQL Server, and MySQL. They have their own characteristics, the differences are as follows:
ORACLE: Oracle is the core product of Oracle. It can run on all mainstream platforms (including windows) and has the highest level of ISO certification in terms of security. Today, the largest database market share is the largest, it has the highest concurrency, the best efficiency, the highest performance, the highest charges, and a high price. It is suitable for large projects of large companies.
DB2: The concurrency and efficiency of IBM's large database products are not as good as that of Oracle, but the core advantage is the powerful data processing in the background, which is also expensive. It can run on all mainstream platforms (including windows) and is most suitable for projects with massive data volumes. It features high online transaction processing performance and has the highest level of ISO certification in terms of security. Large financial-related projects may use two types of databases. Oracle is the first to handle concurrency, and DB2 is responsible for data processing.
SQL Server: Microsoft products can only run on Windows. The interface is friendly, without any openness, and no security certificate is obtained. It is suitable for small and medium-sized projects if multiple users have poor performance.
MySQL: Oracle was incorporated into ORACLE after sun was acquired. It is widely used in small and medium-sized projects, and even large projects use it for database clusters. It is basically free of charge, suitable for personal websites and website applications of some small enterprises.
2. Common RedHat Linux commands
Man RM (Rm -- Help)
View help
CD
Enter the Directory
PS-Ef | grep Java
View Processes
Pstree | grep Java
View process tree
Kill somepid
Kill a process
Kill-9 $ (PS-Ef | grep udpserver | grep Java | awk '{print $2 }')
Delete A udpserver Process
Rpm-AQ | grep PHP
View installation media
PWD
View Current Directory
Ls-l-T
-L display details,-t sort by Time
Ll
Equivalent to LS-l
Find/-name libnativemethod. So
Equivalent to ll | grep somefile
Grep sometext *
Search for all text in the current directory
Ifconfig
IP Address Configuration. You can use the setup command to start the character interface.
Chmod A + x somefile
All users can execute
Chmod U + x somefile
The current user can execute
Env
Environment configuration, equivalent to set in window
Env | grep path
View environment variables
Export
Equivalent to set classpath
Echo
Output variable name
Netstat-NPL
View port
Lsof-I: 22
View port Process
CP from
Copy an object
CP-Fr./j2sdk1.4.2 _ 04/usr/Java
Copy directory
Mkdir
Create directory
MV
Cut or rename
Rm-R
Recursive deletion.-F indicates force.
> Somefile
Clear File Content
Which Java
View the directory corresponding to the Java Process
Who
Show current user
Users
Show current session
Zip-r filename.zip filesdir
Zip a folder
Unzip somefile.zip
Decompress the ZIP file to the current directory.
Gunzip somefile.cpio.gz
Decompress. GZ
Cpio-idmv <somefile. cpio
Cpio operations
PS auxwww | sort-n-r-k 5 | head-5
Sort by resource usage. The first 5 indicates the number of columns, and the second 5 indicates the first few
Hostname-I
Displays the host machine name, adds I, and displays the IP address of ETC/hosts.
Rpm-IVH some. rpm
Install software
Rpm-uvh some. rpm
Update Software
Rpm-Qa | grep somesoftname
Whether a software has been installed
Tar-xvzf some.tar.gz
Extract package
Tar-cvzf some.tar.gz filedir
Compress the package
Shutdown-I6-Y 0
Restart the server immediately
Reboot
Restart the server immediately, equivalent to shutdow-R now
Halt
Shutdown immediately, shutdown-H
Shutdonw-R
Shutdown-R + 15
Shutdonw-R + 30
Timed restart
Gdmsetup
Start the system configuration management interface, which must be executed on the GUI
Setup
Start the text Configuration Management Interface
VI/etc/sysconfig/Network
Modify the machine name, and then restart the machine or service network restart.
Locale
Display System Language
Export lang = zh_cn.gbk
Set the system language to solve consol Chinese garbled characters
Ln-s src_full_file the_link_name
Create soft link
Last
View logged-in user history in reverse order
History
View History commands
Tail-10 somefile
View the last 10 lines of the file
Head-10 somefile
View the first 10 lines of the file
Tail-F somefile
View File Content in real time for debugging
Date-s 10/09/2009
Modification date
Date-s 13:24:00
Modification time. date is displayed directly.
DF-K
View File disk space
DF-V
View a file space
Du
View disk space usage
Free
View memory usage
Top
View the current system resource usage
Vmstat 5 10
Refresh once in less than 5 seconds, refresh 10 times; time, Timex, uptime, iostat, SAR
CAT/proc/cpuinfo | grep processor | WC-l
Obtain the number of CPUs
Service mysqld start
Start the MySQL service.
Service mysqld stop
Stop MySQL Service
Serice mysqld status
Display MySQL service status
Service-status-Al
View existing services
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