Foreword
We have an operating system is to run user programs, run the program requires the mobilization process, so the process management is the heart of any operating system.
In fact, the process is the result of current events program code being executed.
Understand the process
- Process:
the process is a static document, a copy of the running program, and there is a life cycle. - Process Status:
| status | definition |
|---|---|
| R(TASK_RUNNING) | Executable state (RUNNING, READY) |
| S(TASK_INTERRUPTIBLE) | You can wake to sleep |
| D(TASK_UNINTERRUPTIBLE) | Can not wake up from sleep state |
| T(TASK_STOPPED) | Suspended state |
| Z(EXIT_ZOMBIE) | Dead state |
Running andReady stateThe difference is whether it is occupied cpu time slice
Ready state andBe awakeThe difference is whether the run queue in the cpu
You can wake up withNot wake upThe difference is whether the system has the resources needed to run the program.
ctrl + z can process into the backgroundSuspended stateGenerally suspended state is manipulated by man.
Dead stateThis refers to the process of non-parent process to recover their system resources, will result in waste of system resources.
Process Viewer
-
Process Tree pstree
[root@workstation Desktop]# pstree systemd─┬─ModemManager───2*[{ModemManager}] ├─NetworkManager───2*[{NetworkManager}] ├─accounts-daemon───2*[{accounts-daemon}] ├─agetty ├─atd ├─auditd─┬─sedispatch │ └─2*[{auditd}] ├─avahi-daemon───avahi-daemon ├─boltd───2*[{boltd}] ├─chronyd ├─colord───2*[{colord}] ├─crond ├─cupsd ├─dbus-daemon───{dbus-daemon} ├─dnsmasq───dnsmasq ├─firewalld───{firewalld} ...process: Is the smallest unit of resource allocation.
Thread: The object of the kernel scheduler, an independent program counter, process stack, and a set of processes register. For linux, thread is a special process. It is the smallest unit of a running process.
systemdIt is daemon. -
ps command (command displays the current process status)
A display terminal associated with the process (the BSD)
X Show all terminals independent of the process (the BSD)
U user to display the progress status information to classify (the BSD)
F hierarchy display process information[root@workstation Desktop]# ps PID TTY TIME CMD 2499 pts/0 00:00:00 bash 3273 pts/0 00:00:00 ps [root@workstation Desktop]# bash [root@workstation Desktop]# ps PID TTY TIME CMD 2499 pts/0 00:00:00 bash 3288 pts/0 00:00:00 bash 3326 pts/0 00:00:00 ps [root@workstation Desktop]# ps f PID TTY STAT TIME COMMAND 2499 pts/0 Ss 0:00 bash 3288 pts/0 S 0:00 \_ basho specify viewing options pid, COMM, Nice, PRI, pcpu, STAT, ppid
-e show all processes (UINX)
-f Show full format information (UNIX)
-H hierarchy display information about processes
-o designated viewing options, pid, comm, nice,% cpu ,% mem, nice[root@workstation Desktop]# ps axo pid,comm,nice,stat | less PID COMMAND NI STAT 1 systemd 0 Ss 2 kthreadd 0 S 3 rcu_gp -20 I< 4 rcu_par_gp -20 I< 6 kworker/0:0H-kb -20 I< 8 mm_percpu_wq -20 I< 9 ksoftirqd/0 0 S 10 rcu_sched 0 I 11 migration/0 - S 12 watchdog/0 - S 13 cpuhp/0 0 S 14 cpuhp/1 0 S 15 watchdog/1 - SSort according to a parameter:
[root@workstation Desktop]# ps axo pid,comm,%cpu --sort=%cpu(正序，倒序加-号) PID COMMAND %CPU 1 systemd 0.0 2 kthreadd 0.0 3 rcu_gp 0.0 4 rcu_par_gp 0.0 6 kworker/0:0H-kb 0.0 8 mm_percpu_wq 0.0 9 ksoftirqd/0 0.0 10 rcu_sched 0.0 ... -
ps command displays information
[root@workstation Desktop]# ps aux|less USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1 0.1 0.7 244444 13744 ? Ss 00:27 0:03 /usr/lib/systemd/systemd --switched-root --system --deserialize 17 root 2 0.0 0.0 0 0 ? S 00:27 0:00 [kthreadd] root 3 0.0 0.0 0 0 ? I< 00:27 0:00 [rcu_gp] root 4 0.0 0.0 0 0 ? I< 00:27 0:00 [rcu_par_gp] root 6 0.0 0.0 0 0 ? I< 00:27 0:00 [kworker/0:0H-kblockd] root 8 0.0 0.0 0 0 ? I< 00:27 0:00 [mm_percpu_wq] root 9 0.0 0.0 0 0 ? S 00:27 0:00 [ksoftirqd/0] root 10 0.0 0.0 0 0 ? R 00:27 0:00 [rcu_sched] root 11 0.0 0.0 0 0 ? S 00:27 0:00 [migration/0] root 12 0.0 0.0 0 0 ? S 00:27 0:00 [watchdog/0] root 13 0.0 0.0 0 0 ? S 00:27 0:00 [cpuhp/0] root 14 0.0 0.0 0 0 ? S 00:27 0:00 [cpuhp/1] ...
Interpretation of the fields shown in the following table:
| Field | Explanation |
|---|---|
| USER | user name |
| PID | Process id |
| %CPU | cpu Amount Percent |
| %MEM | Memory Amount Percent |
| VSZ | The virtual memory size |
| RSS | Memory resident set size |
| TTY | Character terminal |
| STAT | Process State |
| START | operation hours |
| TIME | Occupancy cpu time |
| COMMAND | Process Name |
-
pgrep
Displays the information process
-u uid displays the specified user process
-U name displays the specified user process
-t tty terminal displays the specified process
-l displays the process name
-a display the full format process name
-P pid show the child process specified processes
such as:[root@workstation Desktop]# id student uid=1000(student) gid=1000(student) groups=1000(student),10(wheel) [root@workstation Desktop]# pgrep -u 1000 3831 [root@workstation Desktop]# pgrep -l -u 1000 3831 bash [root@workstation Desktop]# pgrep -l -U student 3831 bash [root@workstation Desktop]# pgrep -l -t pts/1 3791 bash 3830 su 3831 bash [root@workstation Desktop]# pgrep -la -t pts/1 3791 bash 3830 su - student 3831 -bash [root@workstation Desktop]# pgrep -P 1 621 656 799 811 863 864 868 869 871 872 875 ... [root@workstation Desktop]# pgrep -aP 1 621 /usr/lib/systemd/systemd-journald 656 /usr/lib/systemd/systemd-udevd 799 /usr/bin/rpcbind -w -f 811 /sbin/auditd 863 /usr/lib/systemd/systemd-machined 864 /usr/sbin/mcelog --ignorenodev --daemon --foreground 868 avahi-daemon: running [workstation.local] 869 /usr/libexec/udisks2/udisksd 871 /sbin/rngd -f 872 /usr/libexec/rtkit-daemon 875 /usr/sbin/smartd -n -q never ... -
pidof (pid acquired according to the process name)
For example:[root@workstation Desktop]# watch -n 1 date [root@workstation Desktop]# pidof watch 4166 [root@workstation Desktop]# ps aux|grep watch root 12 0.0 0.0 0 0 ? S 00:27 0:00 [watchdog/0] root 15 0.0 0.0 0 0 ? S 00:27 0:00 [watchdog/1] root 36 0.0 0.0 0 0 ? S 00:27 0:00 [watchdogd] root 4166 0.0 0.1 223888 2844 pts/0 S+ 01:42 0:00 watch -n 1 date root 4375 0.0 0.0 221864 972 pts/2 S+ 01:42 0:00 grep --color=auto watch -
top
top - 01:46:39(当前系统时间) up 1:19(当前系统运行时间), 1 user(当前系统有多少用户正在登录), load average(系统负载): 0.10(一分钟内队列等待数), 0.04(五分钟), 0.01(十五分钟) Tasks(任务): 249 total(总数), 2 running(正在运行数), 247 sleeping, 0 stopped(暂停), 0 zombie %Cpu(s)(cpu使用量): 4.6 us(用户), 1.0 sy(内核), 0.0 ni(调整优先级), 94.1 id(空闲), 0.0 wa(等待输入输出时间), 0.2 hi(硬件中断时间), 0.0 si(软件中断时间), 0.2 st(被偷走的cpu量如虚拟机) MiB Mem(物理内存) : 1829.1 total, 211.9 free, 1003.3 used, 613.9 buff/cache(缓存) MiB Swap(交换内存): 0.0 total, 0.0 free, 0.0 used. 640.1 avail Mem PID（进程号） USER（用户） PR（优先级） NI（优先级代表的nice值） VIRT（vsz虚拟内存） RES（常驻内存地址） SHR（共享资源） S（状态） %CPU（cpu用量） %MEM（内存用量） TIME+ COMMAND（cpu时间即命令名称）top internal parameters:
P cpu by percentage
M memory percentage of
T occupied cpu time accumulated
l turn on / off the uptime information
t on / off task & cpu information
s adjustment of the refresh frequency
k terminate the process
u view specified user process== top command parameters: ==
-d specified refresh interval
-b displayed on a batch
-n shows the number of batch
Process priority
Process the order for possession of resources
- Resource consumption divided according to the type of process
| Resource usage | Process Type |
|---|---|
| cpu intensive use | CPU-Bound |
| I / O-intensive use | I/O-Bound |
-
Priority Range
for Linux priority is divided into a fixed number (0-139)
1-99 have real-time priority, the larger the number the higher the priority, the processing system for personal use without having to manually
100-139 static priority, The smaller the number the higher the priority -
NICE value
NICE value: -20 ~ 19 100 ~ 139 static priority
ordinary users can only lower priority, superuser be adjusted
on command priority
• PS AX -o Nice, PID, COMM
• -n priority Nice program
• reince-n pid priority programs
such as:[root@workstation Desktop]# vim [1]+ Stopped vim [root@workstation Desktop]# ps -o stat,nice,comm,pid STAT NI COMMAND PID Ss 0 bash 2499 S 0 bash 3288 T 0 vim 5343 R+ 0 ps 5350Increased value and nice to look at:
[root@workstation Desktop]# renice -n -10 5343 5343 (process ID) old priority 0, new priority -10 [root@workstation Desktop]# ps -o stat,nice,comm,pid STAT NI COMMAND PID Ss 0 bash 2499 S 0 bash 3288 T< -10 vim 5343 R+ 0 ps 5373Reduce the nice value and view:
[root@workstation Desktop]# renice -n 10 5343 5343 (process ID) old priority -10, new priority 10 [root@workstation Desktop]# ps -o stat,nice,comm,pid STAT NI COMMAND PID Ss 0 bash 2499 S 0 bash 3288 TN 10 vim 5343 R+ 0 ps 5395Open vim into the background and do not take up the terminal:
[root@workstation Desktop]# vim & [2] 5474 [root@workstation Desktop]# ps -o stat,nice,comm,pid STAT NI COMMAND PID Ss 0 bash 2499 S 0 bash 3288 TN 10 vim 5343 T 0 vim 5474 R+ 0 ps 5481 [2]+ Stopped vimAssign priorities and into the background:
[root@workstation Desktop]# nice -n 5 vim & [3] 5511 [root@workstation Desktop]# ps -o stat,nice,comm,pid STAT NI COMMAND PID Ss 0 bash 2499 S 0 bash 3288 TN 10 vim 5343 T 0 vim 5474 TN 5 vim 5511 R+ 0 ps 5518 [3]+ Stopped nice -n 5 vim
Taiwan before and after the process of calling
Related command:
| instruction | meaning |
|---|---|
| jobs | View background tasks |
| ctrl+z | The foreground task into the background |
| bg | Activation daemon |
| fg | Repatriation process |
| & | Runs in the background |
E.g:
[root@workstation Desktop]# jobs
[1] Stopped vim
[2]- Stopped vim
[3]+ Stopped nice -n 5 vim
Graphics and turn into the background:
[root@workstation Desktop]# gedit
^Z
[4]+ Stopped gedit
[root@workstation Desktop]# jobs
[1] Stopped vim
[2] Stopped vim
[3]- Stopped nice -n 5 vim
[4]+ Stopped gedit
Background can activate the wake-up process:
[root@workstation Desktop]# bg 4
[4]+ gedit &
[root@workstation Desktop]# jobs
[1] Stopped vim
[2]- Stopped vim
[3]+ Stopped nice -n 5 vim
[4] Running gedit &
Active background can not be the wake-up process:
[root@workstation Desktop]# bg 1
[1] vim &
[1]+ Stopped vim
bg在此不可使用
[root@workstation Desktop]# fg 1
vim
[root@workstation Desktop]# jobs
[2]- Stopped vim
[3]+ Stopped nice -n 5 vim
signal
- Controllable signal type
man 7 signal See all signal information
| Controllable signal | meaning |
|---|---|
| 1 | Refresh |
| 2 | Keyboard interrupt input |
| 3 | Exit Keyboard |
| 9 | Forced End |
| 15 | Normally closed |
| 18 | Activation process |
| 19 | Forced pause |
| 20 | Normal pause |
-
Command signal
kill signal pid[root@workstation Desktop]# gedit & [1] 9662 [root@workstation Desktop]# kill -9 9662 [1]+ Killed geditkillall signal process name
[root@workstation Desktop]# gedit & [1] 9628 [root@workstation Desktop]# killall -9 gedit [1]+ Killed geditpkill signal conditions (can -help to view)
与pgrep很相似，例如： [root@workstation Desktop]# su - student Last login: Sun Jan 19 01:30:16 EST 2020 on pts/1Open a new shell:
[root@workstation Desktop]# pkill -u 1000Original shell:
[student@workstation ~]$ logout
System daemons
- 守护进程的定义
守护进程就是通常讲Daemon进程,是linux后台执行的服务进程。它独立于控制终端、周期性地执行某种任务或等待处理某些发生事件，不会随终端关闭而停止,直到接受停止信息才会结束。
后记
需要配置网络，才可以做守护进程的实验，所以暂时无法做。
