[svc]centos7的服务治理-systemd

经常用到的高频命令小结

- 所有服务unit放在这里
ll /usr/lib/systemd/system

- 默认启动级别
[root@n1 ~]# ll /etc/systemd/system/default.target 
lrwxrwxrwx 1 root root 41 Mar  4 09:02 /etc/systemd/system/default.target -> /usr/lib/systemd/system/multi-user.target

- 开机启动的服务
ll /etc/systemd/system/multi-user.target.wants/

- 哪些服务开机会启动
[root@n1 ~]# systemctl list-unit-files --type service |grep enable
autovt@.service                               enabled 
crond.service                                 enabled 
docker.service                                enabled 
getty@.service                                enabled 
ntpdate.service                               enabled 
rsyslog.service                               enabled 
sshd.service                                  enabled 
sysstat.service                               enabled 

- 目前哪些服务处于active状态
[root@n1 ~]# systemctl list-units --type service |grep active
crond.service                      loaded active running Command Scheduler
dbus.service                       loaded active running D-Bus System Message Bus
docker.service                     loaded active running Docker Application Container Engine
[e-mail]                 loaded active running Getty on tty1

- 查看某个服务是否开机自启
systemctl is-enabled httpd.service 或
systemctl status httpd.service

systemd 有很多unit,其中service.unit是管理系统服务的.

unit的类型

/usr/lib/systemd/system

查看管理系统服务的相关的, 即 .service后缀的

[root@n1 system]# ls /usr/lib/systemd/system/*.service|more
/usr/lib/systemd/system/arp-ethers.service
/usr/lib/systemd/system/auditd.service
/usr/lib/systemd/system/autovt@.service
/usr/lib/systemd/system/blk-availability.service
/usr/lib/systemd/system/brandbot.service
...

特点:
    不需要可执行权限,其内容也不能执行
    仅是systemd的调用的配置文件

unit类型	作用
Service unit	管理系统服务,我们暂且只关心这个
Target unit	多个Unit构成的一个组
Device Unit	硬件设备
Mount Unit	文件系统的挂载点
Automount Unit	自动挂载点
Path Unit	文件或路径
Scope Unit	不是由 Systemd 启动的外部进程
Slice Unit	进程组
Snapshot Unit	Systemd 快照，可以切回某个快照
Socket Unit	进程间通信的 socket
Swap Unit	swap 文件
Timer Unit	定时器

centos6 chkconfig VS 使用systemd的service unit治理centos7服务

任务	旧指令	新指令
哪些服务正在跑?	chkconfig --list\grep 3:on	systemctl list-units --type=service
哪些服务开机会自启动?	chkconfig --list	systemctl list-unit-files --type=service
使httpd开机自启动	chkconfig --level 3 httpd on	systemctl enable httpd.service
使httd开机不自启动	chkconfig --level 3 httpd off	systemctl disable httpd.service
查看httpd现在是否启动着	service httpd status	systemctl status httpd.service （服务详细信息）
启动某服务	/etc/init.d/httpd start	systemctl start httpd.service
停止某服务	/etc/init.d/httpd stop	systemctl stop httpd.service
重启某服务	/etc/init.d/httpd restart	systemctl restart httpd.service
所有已装载的级别(而非当前级别)	runlevel	systemctl list-units --type target
查看默认级别是啥	cat /etc/inittab	systemctl get-default
设置默认级别	init 3	systemctl set-default multi-user.target
查看服务状态	/etc/init.d/http status	systemctl is-enabled httpd.service/systemctl status httpd.service
默认启动第一个进程	init	systemd

ls /usr/lib/systemd/system/*.service|more 下以service开头的文件,都是和系统服务有关的, 其下还有别的后缀的服务.是别的unit的配置文件.

serivice unit配置

target unit: 的含义是服务组，表示一组服务。

将很多服务放在一坨, 开启启动时候加载这个文件.

启动级别

/usr/lib/systemd/system
/etc/systemd/system

runlevel0.target -> poweroff.target
runlevel2.target -> multi-user.target
runlevel3.target -> multi-user.target
runlevel4.target -> multi-user.target
runlevel5.target -> graphical.target
runlevel6.target -> reboot.target

注意: centos7里,运行级别234没区别.

查看在运行的服务

我们看ACTIVE就ok了,SUB这一列可以不用理会

[root@n1 system]# systemctl list-units --type=service
UNIT                               LOAD   ACTIVE SUB     DESCRIPTION
crond.service                      loaded active running Command Scheduler
dbus.service                       loaded active running D-Bus System Message Bus
docker.service                     loaded active running Docker Application Container Engine
[e-mail]                 loaded active running Getty on tty1
httpd.service                      loaded active running The Apache HTTP Server

查看开机是否会启动

[root@n1 system]# systemctl list-unit-files --type=service
UNIT FILE                                     STATE   
arp-ethers.service                            disabled
auditd.service                                disabled
autovt@.service                               enabled #开机会启动
blk-availability.service                      disabled#开机不会启动
brandbot.service                              static  #这类不用管
conntrackd.service                            disabled

systemd管理服务入门

设置开机自动启动细节

[root@n1 ~]# yum install psmisc -y
[root@n1 ~]# pstree
systemd─┬─agetty
        ├─crond
        ├─dbus-daemon
        ├─dockerd─┬─docker-containe─┬─docker-containe─┬─mysqld───20*[{mysqld}]
        │         │                 │                 └─8*[{docker-containe}]
        │         │                 └─9*[{docker-containe}]
        │         ├─docker-proxy───3*[{docker-proxy}]
        │         └─11*[{dockerd}]
        ├─httpd───8*[httpd]
        ├─lvmetad
        ├─polkitd───5*[{polkitd}]
        ├─rsyslogd───2*[{rsyslogd}]
        ├─sshd───sshd───bash───pstree
        ├─systemd-journal
        ├─systemd-logind
        └─systemd-udevd

[root@n1 system]# systemctl enable httpd
Created symlink from /etc/systemd/system/multi-user.target.wants/httpd.service to /usr/lib/systemd/system/httpd.service.

相当于执行

ln -s /usr/lib/systemd/system/httpd.service /etc/systemd/system/multi-user.target.wants/httpd.service

disable相当于删除

[root@n1 system]# systemctl disable httpd
Removed symlink /etc/systemd/system/multi-user.target.wants/httpd.service.

[root@n1 system]# ll /etc/systemd/system/multi-user.target.wants
total 0
lrwxrwxrwx. 1 root root 37 Dec 27 04:44 crond.service -> /usr/lib/systemd/system/crond.service
lrwxrwxrwx  1 root root 38 Dec 26 21:05 docker.service -> /usr/lib/systemd/system/docker.service
lrwxrwxrwx  1 root root 37 Mar  4 03:39 httpd.service -> /usr/lib/systemd/system/httpd.service
lrwxrwxrwx. 1 root root 39 Dec 26 21:00 ntpdate.service -> /usr/lib/systemd/system/ntpdate.service
lrwxrwxrwx. 1 root root 40 Dec 27 04:44 remote-fs.target -> /usr/lib/systemd/system/remote-fs.target
lrwxrwxrwx. 1 root root 39 Dec 27 04:44 rsyslog.service -> /usr/lib/systemd/system/rsyslog.service
lrwxrwxrwx. 1 root root 36 Dec 27 04:44 sshd.service -> /usr/lib/systemd/system/sshd.service
lrwxrwxrwx. 1 root root 39 Dec 27 05:00 sysstat.service -> /usr/lib/systemd/system/sysstat.service

设置启动级别的命令

- 设置默认启动级别
[root@n1 ~]# systemctl set-default graphical.target 
Removed symlink /etc/systemd/system/default.target.
Created symlink from /etc/systemd/system/default.target to /usr/lib/systemd/system/graphical.target.

- 查看默认的启动级别
[root@n1 ~]# systemctl get-default 
graphical.target

- 手动修改启动级别(先将原来的rm了)
[root@n1 ~]# ln -sv /usr/lib/systemd/system/multi-user.target /etc/systemd/system/default.target
ln: failed to create symbolic link ‘/etc/systemd/system/default.target’: File exists
[root@n1 ~]# rm -rf /etc/systemd/system/default.target
[root@n1 ~]# ln -sv /usr/lib/systemd/system/multi-user.target /etc/systemd/system/default.target
‘/etc/systemd/system/default.target’ -> ‘/usr/lib/systemd/system/multi-user.target’
[root@n1 ~]# systemctl get-default 
multi-user.target

- 查看服务状态
[root@n1 ~]# systemctl is-enabled httpd.service 
disabled