9.28 linux系统基础优化

• 关闭SELinux(是美国安全局对强制访问的实现）功能

[root@wen ~]# sed -i 's#SELINUX=enforcing#SELINUX=disabled#g' /etc/selinux/config            #使用sed + i 命令修改
[root@wen ~]# grep "SELINUX=disabled" /etc/selinux/config                                    #grep查看
SELINUX=disabled
[root@wen ~]# cat /etc/selinux/config

# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=disabled
# SELINUXTYPE= can take one of these two values:
#     targeted - Targeted processes are protected,
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted
以上重启生效，生产环境不能重启

用以下命令不用重启　
[root@wen ~]# getenforce
Enforcing
[root@wen ~]# setenforce
usage: setenforce [ Enforcing | Permissive |  |  ]
[root@wen ~]# setenforce
[root@wen ~]# getenforce
Permissive

• 运行级别

[root@wen ~]# cat /etc/inittab
# inittab is only used by upstart for the default runlevel.
#
# ADDING OTHER CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
#
# System initialization is started by /etc/init/rcS.conf
#
# Individual runlevels are started by /etc/init/rc.conf
#
# Ctrl-Alt-Delete is handled by /etc/init/control-alt-delete.conf
#
# Terminal gettys are handled by /etc/init/tty.conf and /etc/init/serial.conf,
# with configuration in /etc/sysconfig/init.
#
# For information on how to write upstart event handlers, or how
# upstart works, see init(), init(), and initctl().
#
# Default runlevel. The runlevels used are:
#    - halt (Do NOT set initdefault to this)
#    - Single user mode
#    - Multiuser, without NFS (The same as , if you do not have networking)
#    - Full multiuser mode
#    - unused
#    - X11                   #桌面
#    - reboot (Do NOT set initdefault to this)
#
id::initdefault:

[root@wen ~]# grep :initdefault /etc/inittab          #调整运行级别，默认3，可以调成其他
id::initdefault:
[root@wen ~]# runlevel                #查看当前级别
N
[root@wen ~]# init                    #切换运行级别

• 关机

shutdown（halt） init0
参数
-r reboot after shutdown
-h halt or power off after shutdown       

shutdown -h     #10分钟后关闭
shutdown now     #马上
poweroff                #关闭电源

*关闭防火墙
[root@wen ~]# /etc/init.d/iptables stop                     #临时关闭
iptables：将链设置为政策 ACCEPT：filter             [确定]
iptables：清除防火墙规则：                                [确定]
iptables：正在卸载模块：                                   [确定]
[root@wen ~]# /etc/init.d/iptables status                   #查看状态
iptables：未运行防火墙。
[root@wen ~]# /etc/init.d/iptables restart                  # 重启防火墙
iptables：应用防火墙规则：                                [确定]
[root@wen ~]# chkconfig iptables off                         #开机也不启动了

• linux中文显示设置等

*中文显示设置
[root@wen ~]# echo 'LANG="zh_CN.UTF-8“‘ > /etc/sysconfig/i18n
[root@wen ~]# cat /etc/sysconfig/i18n
LANG="zh_CN.UTF-8“
[root@wen ~]# echo $LANG
zh_CN.UTF-
同时调整ssh客户端

*设置账号超时时间
[root@wen ~]# export TMOUT=      #5秒后关机  （临时生效）
[root@wen ~]# timed out waiting for input: auto-logout

*设置命令行历史记录
[root@wen ~]# history -c         #清除所有历史记录
[root@wen ~]# history             #查看历史记录
      history
[root@wen ~]# echo  

[root@wen ~]# echo  

[root@wen ~]# echo  

[root@wen ~]# echo  

[root@wen ~]# echo  

[root@wen ~]# history -d         #删除指定行记录
[root@wen ~]# history
      history
      echo
      echo
      echo
      echo
      history -d
      history
[root@wen ~]# !                 #执行某行历史命令
history -d 

[root@wen ~]# export HISTSIZE=        #控制历史记录记录数量（临时生效）#永久生效放在/etc/profile文件下，然后source以下/etc/profile
[root@wen ~]# history
      history
      echo
      history -d
      export HISTSIZE=
      history
[root@wen ~]# cat ~/.bash_history         #即使控制了在根目录下还有
[root@wen ~]# export HISTORYSIZE=    #命令行命令对应文件的记录数

*隐藏版本信息
[root@wen ~]# cat /etc/issue
CentOS release 6.7 (Final)
Kernel \r on an \m

[root@wen ~]# > /etc/issue
[root@wen ~]# cat /etc/issue.net
CentOS release 6.7 (Final)
Kernel \r on an \m
[root@wen ~]# >/etc/issue.net
[root@wen ~]# cat /etc/issue
[root@wen ~]#