2021-10-31Ubuntu进程、循环任务及系统服务

进程管理

        (1)进程查看

        使用ps命令查看进程：
        ps：表示查看和当前用户有关的进程。

# 使用"ps"命令查看和当前用户有关的进程
fu@fu-virtual-machine:~$ ps
    PID TTY          TIME CMD
   2731 pts/0    00:00:00 bash
   3100 pts/0    00:00:00 ps

        ps -l：查看和当前用户有关进程的详细信息。

# 使用"ps -l"命令查看和当前用户有关进程的详细信息
fu@fu-virtual-machine:~$ ps -l
F S   UID     PID    PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
0 S  1000    2731    2720  0  80   0 -  4845 do_wai pts/0    00:00:00 bash
0 R  1000    3104    2731  0  80   0 -  5017 -      pts/0    00:00:00 ps

        ps -el：查看所有运行进程的详细信息，-e与-A参数作用一样，都是查看全部进程。

# 查看系统中所有运行中进程的详细信息
fu@fu-virtual-machine:~$ ps -el
F S   UID     PID    PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
4 S     0       1       0  0  80   0 - 25510 -      ?        00:00:05 systemd
1 S     0       2       0  0  80   0 -     0 -      ?        00:00:00 kthreadd
1 I     0       3       2  0  60 -20 -     0 -      ?        00:00:00 rcu_gp
1 I     0       4       2  0  60 -20 -     0 -      ?        00:00:00 rcu_par_gp
1 I     0       6       2  0  60 -20 -     0 -      ?        00:00:00 kworker/0:
1 I     0       9       2  0  60 -20 -     0 -      ?        00:00:00 mm_percpu_
# ...此后还有很多运行中进程

        进程详细信息中有PID和PPID两列，分别表示当前进程的编号和启动该进程的父进程编号。

 
 
        使用进程树命令pstree查看进程：
        pstree：以树的组织形式打印系统中运行的所有进程。

# 使用"pstree"命令查看进程树
fu@fu-virtual-machine:~$ pstree
systemd─┬─ModemManager───2*[{
    
    ModemManager}]
        ├─NetworkManager───2*[{
    
    NetworkManager}]
        ├─VGAuthService
        ├─accounts-daemon───2*[{
    
    accounts-daemon}]
        ├─acpid
        ├─avahi-daemon───avahi-daemon
        ├─bluetoothd
        ├─colord───2*[{
    
    colord}]
# ...此后还有很多显示

        pstree -p：在pstree的基础上显示每个进程的PID。

# 查看进程树，带"PID"
fu@fu-virtual-machine:~$ pstree -p
systemd(1)─┬─ModemManager(828)─┬─{
    
    ModemManager}(847)
           │                   └─{
    
    ModemManager}(851)
           ├─NetworkManager(738)─┬─{
    
    NetworkManager}(797)
           │                     └─{
    
    NetworkManager}(808)
           ├─VGAuthService(701)
           ├─accounts-daemon(723)─┬─{
    
    accounts-daemon}(733)
           │                      └─{
    
    accounts-daemon}(804)
# ...此后还有很多显示

    
    
        使用top命令动态监控进程：
        top：动态监控所有进程，使用该命令后，会进入top环境，在该环境中，h表示查看帮助；N表示进程以PID排序显示；P表示进程以按CPU占有率排序显示；M表示进程按内存资源占有率排序显示；T表示进程按使用CPU累计时间排序显示；q表示退出；（注意大小写）

        top -p 1000：动态监控PID为1000的进程状态。

        (2)杀死进程：
        杀死进程的命令为kill
        kill -9 3169：杀死PID为3169的进程。

# 查看和当前用户有关的进程
fu@fu-virtual-machine:~$ ps
    PID TTY          TIME CMD
   2731 pts/0    00:00:00 bash
   3169 pts/0    00:00:00 nano
   3170 pts/0    00:00:00 ps
# 使用"kill"命令杀死进程编号为"3169"的进程
fu@fu-virtual-machine:~$ kill -9 3169
# 成功杀死进程
fu@fu-virtual-machine:~$ ps
    PID TTY          TIME CMD
   2731 pts/0    00:00:00 bash
   3171 pts/0    00:00:00 ps
[1]+  已杀死               nano

循环任务管理

        循环任务管理命令为：crontab。
        crontab -e：创建循环任务；如果第一次执行该命令首先会让用户指定用什么编辑器去编辑/var/spool/cron/crontabs目录下的循环任务文件，这个任务文件名为用户名。

        循环任务文件如下：

# Edit this file to introduce tasks to be run by cron.
# 
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
# 
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').
# 
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
# 
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
# 
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
# 

        创建循环任务的语法为：分 时 日 月 周 命令，周的取值为1-7，即星期一到星期二。

        在以上显示的表示时间的字段可以使用如下符号：
        *：代表所有可能的值，例如月份字段如果是星号，则表示在满足其它字段的制约条件后每月都执行该命令操作。
        ,：可以用逗号隔开的值指定一个列表范围，例如，"1,2,5,7,8,9"。
        -：可以用整数之间的中杠表示一个整数范围，例如"2-6"表示"2,3,4,5,6"。
        /：可以用"/"指定时间的间隔频率，"/"可以和"*"一起使用，例如"*/10"，如果用在分钟字段，表示每十分钟执行一次。

        tty：该命令打印出当前用户bash的终端设备名。

fu@fu-virtual-machine:/var/spool/cron$ tty
/dev/pts/0

        30-50/5 12-13 10 12 * echo Hello! >> /dev/pts/0：表示每年的12月10日的12:30-12:50和13:30-13:50的时间段，每隔5分钟向bash输出Hello!。

        crontab -l：查看任务文件。

fu@fu-virtual-machine:/var/spool/cron$ crontab -l
# Edit this file to introduce tasks to be run by cron.
# 
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
# 
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').
# 
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
# 
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
# 
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
# 
# For more information see the manual pages of crontab(5) and cron(8)
# 
# m h  dom mon dow   command
0-30/5 15-16 * * * echo "Auto print Hello!" >> /dev/pts/0

        crontab -r：清除任务。

# 查看任务文件的最后一行
fu@fu-virtual-machine:/var/spool/cron$ sudo tail -n 1 /var/spool/cron/crontabs/fu
[sudo] fu 的密码： 
0-30/5 15-16 * * * echo "Auto print Hello!" >> /dev/pts/0

# 清除任务
fu@fu-virtual-machine:/var/spool/cron$ crontab -r
# 清除成功
fu@fu-virtual-machine:/var/spool/cron$ crontab -l
no crontab for fu

系统服务

        系统服务的命令为：systemctl
        systemctl status crontab：查看cron服务的状态。

# 查看"cron"服务的状态
fu@fu-virtual-machine:/var/spool/cron$ systemctl status cron
● cron.service - Regular background program processing daemon
     Loaded: loaded (/lib/systemd/system/cron.service; enabled; vendor preset: >
     Active: active (running) since Sat 2021-10-30 16:37:46 CST; 23h ago
       Docs: man:cron(8)
   Main PID: 734 (cron)
      Tasks: 1 (limit: 2196)
     Memory: 560.0K
     CGroup: /system.slice/cron.service
             └─734 /usr/sbin/cron -f

10月 31 16:25:01 fu-virtual-machine CRON[3736]: pam_unix(cron:session): session>
10月 31 16:25:01 fu-virtual-machine CRON[3738]: (fu) CMD (echo "Auto print Hell>
10月 31 16:25:01 fu-virtual-machine CRON[3736]: pam_unix(cron:session): session>
10月 31 16:30:01 fu-virtual-machine CRON[3791]: pam_unix(cron:session): session>
10月 31 16:30:01 fu-virtual-machine CRON[3794]: (root) CMD ([ -x /etc/init.d/an>
10月 31 16:30:01 fu-virtual-machine CRON[3791]: pam_unix(cron:session): session>
10月 31 16:36:01 fu-virtual-machine cron[734]: (fu) RELOAD (crontabs/fu)
10月 31 16:36:01 fu-virtual-machine CRON[3833]: pam_unix(cron:session): session>
10月 31 16:36:01 fu-virtual-machine CRON[3834]: (fu) CMD (echo "Hello" > /dev/p>
10月 31 16:36:01 fu-virtual-machine CRON[3833]: pam_unix(cron:session): session>
lines 1-20/20 (END)

        systemctl stop cron：停止cron服务。

# 停止"cron"服务
fu@fu-virtual-machine:~$ systemctl stop cron

# 查看"cron"服务的状态
fu@fu-virtual-machine:~$ systemctl status cron
● cron.service - Regular background program processing daemon
     Loaded: loaded (/lib/systemd/system/cron.service; enabled; vendor preset: >
     Active: inactive (dead) since Sun 2021-10-31 16:38:56 CST; 14s ago
       Docs: man:cron(8)
    Process: 734 ExecStart=/usr/sbin/cron -f $EXTRA_OPTS (code=killed, signal=T>
   Main PID: 734 (code=killed, signal=TERM)

10月 31 16:36:01 fu-virtual-machine CRON[3833]: pam_unix(cron:session): session>
10月 31 16:37:01 fu-virtual-machine CRON[3842]: pam_unix(cron:session): session>
10月 31 16:37:01 fu-virtual-machine CRON[3843]: (fu) CMD (echo "Hello" > /dev/p>
10月 31 16:37:01 fu-virtual-machine CRON[3842]: pam_unix(cron:session): session>
10月 31 16:38:01 fu-virtual-machine CRON[3844]: pam_unix(cron:session): session>
10月 31 16:38:01 fu-virtual-machine CRON[3845]: (fu) CMD (echo "Hello" > /dev/p>
10月 31 16:38:01 fu-virtual-machine CRON[3844]: pam_unix(cron:session): session>
10月 31 16:38:56 fu-virtual-machine systemd[1]: Stopping Regular background pro>
10月 31 16:38:56 fu-virtual-machine systemd[1]: cron.service: Succeeded.
# "Stopped"表示该服务被停止了
10月 31 16:38:56 fu-virtual-machine systemd[1]: Stopped Regular background prog>
lines 1-17/17 (END)

        systemctl start cron：表示启动cron服务。

# 启动"cron"服务
fu@fu-virtual-machine:~$ systemctl start cron

# 查看"cron"服务的状态
fu@fu-virtual-machine:~$ systemctl status cron
● cron.service - Regular background program processing daemon
     Loaded: loaded (/lib/systemd/system/cron.service; enabled; vendor preset: >
     Active: active (running) since Sun 2021-10-31 16:41:42 CST; 6s ago
       Docs: man:cron(8)
   Main PID: 3880 (cron)
      Tasks: 1 (limit: 2196)
     Memory: 360.0K
     CGroup: /system.slice/cron.service
             └─3880 /usr/sbin/cron -f
# "Started"表示启动了服务
10月 31 16:41:42 fu-virtual-machine systemd[1]: Started Regular background prog>
10月 31 16:41:42 fu-virtual-machine cron[3880]: (CRON) INFO (pidfile fd = 3)
10月 31 16:41:42 fu-virtual-machine cron[3880]: (CRON) INFO (Skipping @reboot j>
lines 1-13/13 (END)

        systemctl restart cron：表示重新启动cron服务。

# 查看"cron"服务的状态，现在时停止状态
fu@fu-virtual-machine:~$ systemctl status cron
● cron.service - Regular background program processing daemon
     Loaded: loaded (/lib/systemd/system/cron.service; enabled; vendor preset: >
     Active: inactive (dead) since Sun 2021-10-31 16:44:40 CST; 8s ago
       Docs: man:cron(8)
    Process: 3913 ExecStart=/usr/sbin/cron -f $EXTRA_OPTS (code=killed, signal=>
   Main PID: 3913 (code=killed, signal=TERM)

10月 31 16:44:20 fu-virtual-machine systemd[1]: Started Regular background prog>
10月 31 16:44:20 fu-virtual-machine cron[3913]: (CRON) INFO (pidfile fd = 3)
10月 31 16:44:20 fu-virtual-machine cron[3913]: (CRON) INFO (Skipping @reboot j>
10月 31 16:44:40 fu-virtual-machine systemd[1]: Stopping Regular background pro>
10月 31 16:44:40 fu-virtual-machine systemd[1]: cron.service: Succeeded.
# 停止
10月 31 16:44:40 fu-virtual-machine systemd[1]: Stopped Regular background prog>
# 重启"cron"服务
fu@fu-virtual-machine:~$ systemctl restart cron
# 查看"cron"服务的状态
fu@fu-virtual-machine:~$ systemctl status cron
● cron.service - Regular background program processing daemon
     Loaded: loaded (/lib/systemd/system/cron.service; enabled; vendor preset: >
     Active: active (running) since Sun 2021-10-31 16:45:03 CST; 7s ago
       Docs: man:cron(8)
   Main PID: 3937 (cron)
      Tasks: 1 (limit: 2196)
     Memory: 360.0K
     CGroup: /system.slice/cron.service
             └─3937 /usr/sbin/cron -f

# "Started"，重启成功
10月 31 16:45:03 fu-virtual-machine systemd[1]: Started Regular background prog>
10月 31 16:45:04 fu-virtual-machine cron[3937]: (CRON) INFO (pidfile fd = 3)
10月 31 16:45:04 fu-virtual-machine cron[3937]: (CRON) INFO (Skipping @reboot j>

        systemctl disable cron：禁用cron服务。
        systemctl enable cron：使cron服务可用。

        systemctl list-units：列出正在运行的服务

# 列出正在运行的服务
fu@fu-virtual-machine:~$ systemctl list-units | grep cron
  cron.service                                                                                             loaded active running   Regular background program processing daemon                                                                     
  anacron.timer                                                                                            loaded active waiting   Trigger anacron every hour