A, Linux kernel version
1, Linux distributions
Linux distribution = Linux kernel + application
Redhat, CentOS, Ubuntu, Suse, Red Flag, Mint, Fedora
CentOS: Community Edition operating system (free)
Redhat: Enterprise Edition operating system (surcharge)
2, Linux kernel version
Architecture (order from bottom to top): Hardware → kernel → shell → instruction
shell: kernel instructions translated into commands recognizable.
kernel (kernel) .xyz
x: large kernel version number
y: small kernel version: odd, development version; even, stable version
z: the number of patches
Viewing the kernel information: uname -a
View the current release number: cat / etc / redhat-release
Public GPL software license agreement for the software license agreement of open source software.
Two, Linux some simple commands
Turn off the firewall
1. Check the firewall status
systemctl status firewalld
2, turn off the firewall
systemctl stop firewalld
3, disable the firewall boot from Kai
systemctl disable firewalld
4. If you turn on the firewall
systemctl start firewalld
Close selinux
1, edit the configuration file selinux
nano /etc/selinux/config
2, the SELINUX = Eenforcing to SELINUX = disabled
3, Ctrl + x → Y → Enter input
4, restart reboot
5, view the current status selinux
getenforce
If SELINUX = disabled closed on behalf of success.
Shutdown and restart
1, exit the current user's login (logout)
exit
2, the shutdown command
halt -p
poweroff
init 0
shutdown -h (after sending broadcast inform shutdown time, 1min default off)
3, restart command
reboot
init 6
shutdown -r
Linux系统运行级别
0 关机
1 单用户
2 多用户（无NFS）
3 多用户（字符界面下）
4 未定义
5 图形化
6 重启
切换系统运行级别：init 运行级别