安装完CentOS 7 minimal后，无力吐槽，变化之大，发现以前常用的一些命令都没有。
一、常用命令安装
查看anaconda-ks.cfg，原来是没装base group的包
[root@centos7 ~]# cat anaconda-ks.cfg
#version=RHEL7
# System authorization information
auth --enableshadow --passalgo=sha512
# Use CDROM installation media
cdrom
# Run the Setup Agent on first boot
firstboot --enable
ignoredisk --only-use=sda
# Keyboard layouts
keyboard --vckeymap=us --xlayouts='us'
# System language
lang en_US.UTF-8 --addsupport=zh_CN.UTF-8
# Network information
network --bootproto=dhcp --device=eno16777736 --onboot=off --ipv6=auto
network --hostname=localhost.localdomain
# Root password
rootpw --iscrypted
# System timezone
timezone Asia/Chongqing --isUtc --nontp
# System bootloader configuration
bootloader --location=mbr --boot-drive=sda
autopart --type=lvm
# Partition clearing information
clearpart --none --initlabel
%packages
@core # 这里只有core
%end
[root@centos7 ~]# yum groupinstall base # 安装完后ifconfig、service、chkconfig等命令就都有了。
二、运行级别切换
[root@centos7 ~]# cat /etc/inittab # 系统运行级别的设置方式也变化了
# inittab is no longer used when using systemd.
#
# ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
#
# Ctrl-Alt-Delete is handled by /etc/systemd/system/ctrl-alt-del.target
#
# systemd uses 'targets' instead of runlevels. By default, there are two main targets:
#
# multi-user.target: analogous to runlevel 3
# graphical.target: analogous to runlevel 5
#
# To set a default target, run:
#
# ln -sf /lib/systemd/system/<target name>.target /etc/systemd/system/default.target
这里写的很明白了，做个软链修改默认运行级别
[root@centos7 system]# ll /lib/systemd/system/runlevel*.target # 系统0-6 7个运行级别，2 3 4 运行指向同一个文件
lrwxrwxrwx 1 root root 15 Oct 11 03:51 /lib/systemd/system/runlevel0.target -> poweroff.target
lrwxrwxrwx 1 root root 13 Oct 11 03:51 /lib/systemd/system/runlevel1.target -> rescue.target
lrwxrwxrwx 1 root root 17 Oct 11 03:51 /lib/systemd/system/runlevel2.target -> multi-user.target
lrwxrwxrwx 1 root root 17 Oct 11 03:51 /lib/systemd/system/runlevel3.target -> multi-user.target
lrwxrwxrwx 1 root root 17 Oct 11 03:51 /lib/systemd/system/runlevel4.target -> multi-user.target
lrwxrwxrwx 1 root root 16 Oct 11 03:51 /lib/systemd/system/runlevel5.target -> graphical.target
lrwxrwxrwx 1 root root 13 Oct 11 03:51 /lib/systemd/system/runlevel6.target -> reboot.target
三、systemctl管理系统服务
systemctl可以看作是service和chkconfig的组合
job
chkconfig、service systemctl
服务开机自启动 chkconfig --level 3 httpd on systemctl enable httpd
服务不开机自启动 chkconfig --level 3 httpd off systemctl disable httpd
服务状态
service httpd status
systemctl status httpd(服务详细信息)
systemctl is-active httpd(只显示是否active)
所有服务的启动状态 chkconfig --list systemctl list-units --type=service
启动服务 service httpd start systemctl start httpd
停止服务 service httpd stop systemctl stop httpd
重启服务 service httpd restart systemctl restart httpd
centos 7之前的版本都采用Sysvinit的系统启动进程管理体系，因为是串行的进程启动流程，可能因为某个进程的阻塞而影响启动过程。centos 7使用systemd。目标是尽可能启动更少进程；尽可能将更多进程并行启动（这是性能优于SysVinit的理念基础）。