以下是对新装的linux系统做的一些基本优化，仅供参考！
关闭Selinux
方法一：用vi /etc/selinux/config修改
[root@liangenyu ~]# vi /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
2.方法二：
sed -i s:替换并且修改文件
[root@liangenyu ~]# sed -i 's/SELINUX=enforcing/SELINUX=disabled/' /etc/selinux/config
查看一下配置是否成功？
[root@liangenyu ~]# grep SELINUX=disabled /etc/selinux/config SELINUX=disabled
因为修改了配置需要重启才生效，工作中不可能经常重启系统，我们也将临时生效修改下！
[root@liangenyu ~]# setenforce 0[root@liangenyu ~]# getenforce Permissive
修改系统启动模式：
runlevel: 查看运行级别
init: 切换运行级别
[root@liangenyu ~]# runlevel N 3
不同模式切换：
init 0 重启
init 3 命令行模式
init 5 图形模式
用vi永久修改默认运行级别：
[root@liangenyu ~]# vi /etc/inittab # Default runlevel. The runlevels used are:# 0 - halt (Do NOT set initdefault to this) 关机# 1 - Single user mode 单用户模式# 2 - Multiuser, without NFS (The same as 3, if you do not have networking) 多用户模式# 3 - Full multiuser mode 命令行模式# 4 - unused 不常用# 5 - X11 图形模式# 6 - reboot (Do NOT set initdefault to this) 重启id:3:initdefault: 这里默认是第3命令行模式
精简启动程序：
前期需要启动的四个基本服务：crond network rsyslog ssh
查看级别3启动的服务名称：
[root@liangenyu ~]# LANG=en[root@liangenyu ~]# chkconfig --list|grep "3:on"NetworkManager 0:off1:off2:on3:on4:on5:on6:offabrt-ccpp 0:off1:off2:off3:on4:off5:on6:offabrtd 0:off1:off2:off3:on4:off5:on6:offacpid 0:off1:off2:on3:on4:on5:on6:offatd 0:off1:off2:off3:on4:on5:on6:offauditd 0:off1:off2:on3:on4:on5:on6:offautofs 0:off1:off2:off3:on4:on5:on6:offblk-availability0:off1:on2:on3:on4:on5:on6:offbluetooth 0:off1:off2:off3:on4:on5:on6:offcertmonger 0:off1:off2:off3:on4:on5:on6:offcpuspeed 0:off1:on2:on3:on4:on5:on6:offcrond 0:off1:off2:on3:on4:on5:on6:offcups 0:off1:off2:on3:on4:on5:on6:offhaldaemon 0:off1:off2:off3:on4:on5:on6:off
写个脚本一键完成处理：
[root@liangenyu ~]# vim serviceoff.sh#/bin/bashLANG=enfor liangenyu in `chkconfig --list|grep 3:on|awk '{print $1}'`;do chkconfig --level 3 $liangenyu off;donefor liangenyu in crond network rsyslog sshd;do chkconfig --level 3 $liangenyu on; [root@liangenyu ~]# chkconfig --list|grep "3:on"crond 0:off1:off2:on3:on4:on5:on6:offnetwork 0:off1:off2:on3:on4:on5:on6:offrsyslog 0:off1:off2:on3:on4:on5:on6:offsshd 0:off1:off2:on3:on4:on5:on6:off
脚本二：
[root@liangenyu ~]# vim serviceon.sh #!/bin/bashfor liangenyu in `chkconfig --list|grep "3:on"|awk '{print $1}'|grep -vE "crond|network|sshd|rsyslog"`;do chkconfig $liangenyu off;done 执行脚本，并且查看已成功！
[root@liangenyu ~]# ./serviceon.sh [root@liangenyu ~]# chkconfig --list|grep "3:on"crond 0:off1:off2:on3:on4:on5:on6:offnetwork 0:off1:off2:on3:on4:on5:on6:offrsyslog 0:off1:off2:on3:on4:on5:on6:offsshd 0:off1:off2:on3:on4:on5:on6:off
更改SSH服务远程登录配置：
linux远程默认端口：22
默认超级用户:root
[root@liangenyu ~]# vim /etc/ssh//ssh_config #$OpenBSD: sshd_config,v 1.80 2008/07/02 02:24:18 djm Exp $# This is the sshd server system-wide configuration file. See# sshd_config(5) for more information.# This sshd was compiled with PATH=/usr/local/bin:/bin:/usr/bin# The strategy used for options in the default sshd_config shipped with# OpenSSH is to specify options with their default value where# possible, but leave them commented. Uncommented options change a# default value.
Port 52113 修改端口为52113#Port 22 提示默认端口是22#AddressFamily any#ListenAddress 0.0.0.0#ListenAddress ::# To disable tunneled clear text passwords, change to no here!#PasswordAuthentication yesPermitEmptyPasswords no 改为不允许空密码登录PasswordAuthentication yes#LoginGraceTime 2mPermitRootLogin no ssh远程不能用root登录#StrictModes yes#MaxAuthTries 6#MaxSessions 10
#AllowAgentForwarding yes#AllowTcpForwarding yes#GatewayPorts no#X11Forwarding noX11Forwarding yes#X11DisplayOffset 10#X11UseLocalhost yes#PrintMotd yes#PrintLastLog yes#TCPKeepAlive yes#UseLogin no#UsePrivilegeSeparation yes#PermitUserEnvironment no#Compression delayed#ClientAliveInterval 0#ClientAliveCountMax 3#ShowPatchLevel noUseDNS no DNS改为no#PidFile /var/run/sshd.pid#MaxStartups 10#PermitTunnel no#ChrootDirectory none
/etc/init.d/sshd restart==service sshd restart[root@liangenyu ssh]# service sshd restart停止 sshd： [确定]正在启动 sshd： [确定]