Linux process management
- The meaning of the process
- Process status
- ps command style
- ps command display information
- Process filtering command pgrep
- Usage of top command
- Process priority and NICE value
- Front and back calls of the process
- Daemon systemd and systemctl management commands
- Process signals and signal commands
- Login audit in the system
The meaning of the process
A process (process) is a static file, a copy of a program, which has a life cycle, preparation period-running period-termination period.
Process status
| status | definition |
|---|---|
| R（TASK_RUNNING） | Executable state (RUNNING, READING) |
| S(TASK_INTERRUPTIBLE) | Can wake up to sleep |
| D（TASK_UNINTEERUPTIBLE） | Can not wake up sleep state |
| T(TASK_STOPPED) | Suspended state |
| Z(EXIT_ZOMBIE) | Dead state |
ps command style
Divided into three types: BSD, unix, GUN
BSD style
a(显示与终端相关的进程)
x(显示与终端无关的进程)
u(以用户未归类信息显示进程状态信息)
f(层级结构显示进程信息)
o(显示指定参数的进程信息)
unix style:
-e(显示所有进程)
-f(显示完整格式信息)
-H(层级结构显示进程相关信息)
-o(查看指定选项信息)
ps command display information
| Field | Explanation |
|---|---|
| USER | user name |
| PID | Process id |
| %CPU | CPU usage |
| %MEM | Memory usage |
| VSZ | Occupied virtual memory size |
| RSS | Resident memory size |
| TTY | Character terminal |
| STAT | Process status |
| START | operation hours |
| TIME | CPU time |
| COMMAND | Process name |
ps sorting display information
Display the last 6 lines of the positive order command: ps axo pid,comm,%cpu --sort=%cpu | tail -n 6
Display the first 6 lines of the reverse order:ps axo pid,comm,%cpu --sort=-%cpu | head -n 7
Process filtering command pgrep
pgrep 显示指定进程信息
- u id号 显示指定用户进程
- U name 显示指定用户进程
- t tty 显示指定终端进程
- l 显示进程名称
- a 显示完整格式进程名
- P pid 显示指定进程的子进程
pidof 进程名 查看进程id
Usage of top command
- top
- 外部参数
- -d 显示刷新时间
- -b 以批次显示
- -n 显示批次数量
- top内部参数
- P cpu百分比排序
- M 内存百分比排序
- T 累计占用cpu时间
- l 开启或者关闭uptime信息
- t 开启或关闭task&cpu信息
- s 调整刷新频率
- k 终止进程
- u 查看指定用户进程
Process priority and NICE value
- 优先级范围：
- 对于Linux来说，优先级被划分为固定个数（0-139）
- 0-99为实时优先级，数字越大优先级越高，系统自己调用。
- 100-139，为静态优先级，数字越小，优先级越高。
- NICE值
- -20-19对应静态优先级
- 关于优先级命令
- nice -n 优先级 程序名 （手动设置程序优先级）
- renice -n 优先级 程序pid （修改优先级）
| S | Process status |
|---|---|
| I | There is a locked space in the memory (the system is not reclaimed during sleep) |
| N | Low priority |
| < | High priority |
| + | In the foreground (running) |
| s | Top-level process |
| T | stop |
| S | Sleep |
| R | Running |
Front and back calls of the process
| jobs | View background tasks |
|---|---|
| ctrl+z | Break the program into the background and pause the task |
| bg | Activate daemon |
| fg | Call back to the program |
| & | The program runs in the background |
Daemon systemd and systemctl management commands
The daemon, which shares the program control program for the kernel, usually pid is 1
systemctl management system service
- systemctl
- 参数：start ##开启服务
- stop ##停止服务
- reload ##重新加载服务
- restart ##重启服务
- list-units ##查看所有服务当前状态
- list-unit-files ##查看服务开机状态
- list-dependencies ##查看服务依赖性
- enable ##开机自启动服务
- enable --now ##开机自启动并且现在就开启服务
- disable ##开机不自启动服务
- status ##查看服务状态
- mask ##冻结服务
- unmask ##解冻
- set-default ##设定系统运行模式
- ##multi-user.target 无图形界面
- ##graphical.target 有图形界面
- get-default ##查看系统运行模式
- ##0关机 1单用户root模式 2-4无图形界面模式 5图形界面模式 6 重启
Process signals and signal commands
Controllable signal type man 7 signal
| Controllable signal | meaning |
|---|---|
| 1 | Refresh (let the process re-read the configuration, equivalent to systemctl reload) |
| 2 | Clear the process data in the memory |
| 3 | ctrl+/Pause the use of the mouse |
| 9 | Forced end |
| 15 | Normal shutdown |
| 18 | Activation process |
| 19 | Forcibly pause the process |
| 20 | Normal pause |
Signal command:
信号指令：
kill 信号 pid
killall 信号 进程名
pkill 信号 进程名字
Login audit in the system
- w 显示正在登陆系统的账号
- -i 显示登陆来源
- /var/run/utmp
- last 登陆成功现在已经退出的
- /var/log/wtmp
- lastb 试图登录但未成功
- /var/log/btmp