Linux

Administrator root,0Normal User 1-65535System User 1-499 (CENTOS6), 1-999 (CENTOS7)Login User (CENTOS6) +, + (CENTOS7) +/ETC/PASSWD Users and attributes/etc/group groups and attributes/etc/shadow User passwords and attributes/etc/gshadow group

vim /etc/sysctl.confnet.ipv4.tcp_syncookies = 1# indicates that syn cookies is turned on. When a SYN wait queue overflow occurs, cookies are enabled to protect against a small number of SYN attacks, which by default is 0, which is off.

First, user managementThe main 3 A on Linux systems is: Authentication certified Authorization Authorized accouting Audit.Categories of users:In centos6.x/7.xadmin: Root, 0Normal Users: 1-65535System users: 1-499, 1-999 usually

The TR command can replace, compress, and delete characters from standard input. It can literal a group of characters into another set, and is often used to write graceful single-line commands that are powerful.TR (option) (parameter)-C

The./configure is used to detect the target characteristics of your installation platform. For example, it detects if you have CC or GCC, does not need CC or GCC, it is a shell script.Make is used to compile, it reads the instruction from the

　 To learnLinuxshell language, with the most difficult the most primitive, with the people are experts, history at least also have to 30 years, No matter what 3,721 comes up, knock ls  First look at what's in the current directory. A professional

What's the relationship between Linux and Rhel and CentOS?Linux is an open source, free kernel program, is a UNIX like operating system, it is used to manage hardware, and can freely allocate hardware resources, hide the underlying complexity and

There are two types of users in Linux, ordinary users ($) and Superuser root (#), each user has a unique user ID (UID), and each group has a unique group ID (GID).The UID and GID of the Superuser are fixed at 0, and there are some special users in

If the machine service uses Yum source installation, you can download the Lrzsz file before uploading the installation.Step One:Download Lrzsz's tar package first: wget https://ohse.de/uwe/releases/lrzsz-0.12.20.tar.gzStep Two:1) upload the

1. Check the number of physical, the number of cores, the number of logic#total number of cores = number of physical CPUs X number of cores per physical CPU#Total Logical CPUs = number of physical CPUs x number of cores per physical CPU X number of

Paths are divided into relative paths and absolute paths:Relative path: Full path from/startAbsolute path: The path starting from the current directoryRoot: admin (#)Normal User ($)Virtual Network parameters:/: Root/root: User Home Directory/boot:

Error Description:Using Df-i to view the disk I node information, I found that the utilization rate of 98%, the system disk space, there are many, indicating that a large number of filesTroubleshooting ideas:One, timed tasks generate a lot of

Automatic Login: Change etc/gdm/custom.confincrease under [daemon]Automaticloginenable=trueautomaticlogin= (user name)* Valid only when booting with graphical interfaceInstalling the software or changing the configuration usually requires an

1.I/O Redirect: input, output, let's take a look at those inputs that are output: the input data stream: keyboard; Output Data flow:----> Standard output (stdout) display;Incorrect output stream:----> Error output (stderr) display;2. In the shell,

1. Use the JDK package that WINSCP will install to upload to Linux.2. Command TAR-ZXVF [JDK installation package], the installation package must be a tar package before the line.EP:TAR-ZXVF server-jre-7u80-linux-x64.tar.gz3. The installation is

Port:Number of ports: 0-2^16-1 (0-65535) → restricted by TCP, UDP protocol headerftp:20 21Ssh:22Telnet:23dns:53http:80→https:443Smtp:25pop3:110Netstat-an #列出当前的所有网络连接状态-A: Lists all connection statuses, including Tcp/udp/unix sockets-N: Displays the

Recently in the study of Linux, Daoteng a half-day. Finally, the JDK is installed, write a blog record, the key is the JDK environment variable configuration and save theI used the SECURECRT to connect Linux, and then securecrt on the command, about

System configuration and view information related commands# uname-a # View kernel/Os/cpu information# head-n 1/etc/issue # view OS version# cat/proc/cpuinfo # View CPU Information# hostname # View computer name# LSPCI-TV # list all PCI devices#

Use the echo command to display the arrangement of small stars650) this.width=650; "Src=" Http://s5.51cto.com/wyfs02/M01/84/EA/wKiom1eXGz6TsGMaAABIg0Au4oA102.png-wh_500x0-wm_3 -wmp_4-s_2024578408.png "Title=" _ (rijp3118c{' Jg9[ycqxhg.png "alt="

Linux distributions, software installation sources=================================================================1. BackupMv/etc/yum.repos.d/centos-base.repo/etc/yum.repos.d/centos-base.repo.backup---------------------------------------------------