First, what is the process
Program is a static file on disk, the process is a copy of the running program, the process is dynamic, when the program is loaded onto the disk, the program has become a process. The process is the presence of the life cycle, there is preparation, and to terminate run-on
Status Second, the process
| status | definition |
|---|---|
| R(Running) | Executable state (Running, Ready) |
| S(Interruptible) | Be awake |
| D(Uninterruptible) | Not awake |
| T(Stopped) | Suspended state |
| Z(Zombie) | Dead state |
Third, the process of viewing
1, view the process tree
Command pstree, the process is a program that runs the form in the system, by state information view the process, we can understand the system resources occupied by the process of running state of the system is analyzed, adjusted, so that the system remains in a stable operational state
2, display the current status of the command execution process
Command ps(Process Status) can list and process information related to this landing system
- BSD style
| a | Display terminal associated with the process |
|---|---|
| x | Display all associated with a terminal process |
| in | In order to classify the user to display the process status information |
| f | Hierarchy display process information |
| O | Designated viewing options |
- unix style
| -e | Show all processes |
|---|---|
| -f | Show full format information |
| -H | Information about the structure of the display process hierarchy |
| -The | Specifies an option |
- ps command displays information
| Field | Explanation |
|---|---|
| USER | user name |
| PUD | 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 |
3, displays the specified process information
Commandpgrep
| u (uid) | Displays the specified user process |
|---|---|
| -U(name) | Displays the specified user process |
| -t(tty) | Displays the terminal process |
| -l | Displayed process name |
| -a | Show full format process name |
| -P(pid) | Display child processes specified process |
Cut student users view user id and
view the process id
display terminal pts / 1 Terminal Process
display the full format process name
display child processes
4, according to obtain the pid process name
Commandpidof
5, dynamic display memory process information
Commandtop
- 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/关闭uptime信息 |
| t | 开启/关闭task&cpu时间 |
| s | 调整刷新频率 |
| k | 终止进程 |
| u | 查看指定用户进程 |
top命令
关闭uptime信息
关闭task&cpu时间状态1
关闭task&cpu时间状态2
关闭task&cpu时间状态3
调整刷新频率
查看student用户进程信息
终止firellwd进程
- 命令参数
| -d | 指定刷新间隔 |
|---|---|
| -b | 以批次方式显示 |
| -n | 显示批次数量 |
- top显示进程信息详解
top 系统当期时间
up 系统运行时常
user 登录当前系统的用户数量
load average 平均负载1分钟 5分钟 15分钟的队列长度
task 任务
%cpu cpu占用百分比
mem 物理内存
swap 交换分区
其中%cpu中不同参数的含义如下
| us | 用户空间 |
|---|---|
| sy | 内核空间 |
| ni | nice调整时间 |
| id | 空闲时间 |
| wa | 等待io |
| hi | 处理硬件中断 |
| si | 处理软件中断 |
| st | 被虚拟化程序占用的百分比 |
四、进程优先级
-
优先级范围
在Linux中优先级由固定的数字表示（0-139），其中1-99为实时优先级，数字越大优先级越高，是系统自用的，不用手动处理，100-139为静态优先级，数字越小优先级越高 -
NICE值
用数字-20-19对应静态优先级，普通用户只能够调低优先级而超级用户可以任意调整
用ps ax -o nice,pid,comm可以查看系统中进程的优先级
用nice -n 优先级数字 程序以及renice -n 优先级 程序pid可以调整进程的优先级
五、进程的前后台调用
| 指令 | 含义 |
|---|---|
| jobs | 查看后台任务 |
| ctrl+z | 将前台运行程序打入后台 |
| bg | 激活后台进程 |
| fg | 调回进程 |
| & | 运行在后台 |
将gedit调回前台，状态变为running
不能通过bg指令将vim激活，它会立即回到stopped状态
六、信号
- 可控信号类型
命令为man 7 signal
| 可控信号 | 含义 |
|---|---|
| 1 | 刷新 |
| 2 | 中断键盘输入 |
| 3 | 退出键盘 |
| 9 | 强制结束 |
| 15 | 正常关闭 |
| 18 | 激活进程 |
| 19 | 强制暂停 |
| 20 | 正常暂停 |
信号指令为
kill 信号 pid
pkill 信号 进程名称
七、系统守护进程
守护进程是linux后台执行的服务进程，是独立于控制终端，周期性地执行某种任务或等待处理某些发生事件，不会随着终端关闭而停止，直到接受停止信息才会结束
- 守护进程的类型
| 守护进程类型 | 使用系统及特点 |
|---|---|
| Sysv init | 沿用到rehl6 链式开启 |
| upstart | 在rehl6中应用并行启动 |
| systemd | rhel7后使用独立完成启动 |
- systemctl 用法
| 指令 | 用途 |
|---|---|
| systemctl list-unit-files --type=service | 查看服务开机运行情况 |
| systemctl list-units --type=service | 查看服务当前运行情况 |
| systemctl list-dependencies | 查看服务依赖性 |
| systemctl status service | 查看服务状态 |
| systemctl start service | 开启服务 |
| systemctl stop service | 关闭服务 |
| systemctl restart service | 重新启动服务 |
| systemctl enable service | 设定服务开机启动 |
| systemctl disable service | Power shut down service set |
| systemctl enable --now service | Set service start-up and open the service |
| systemctl set-default multi-user.target | Set the system run level is no graphics mode network |
| systemctl set-default graphical.target | Set the system to run level graphics mode network |
Check the operation of the service startup
to view the service is currently running situation
see sshd service dependency
view sshd status display is running and the boot does not start
stopping sshd
later when sshd service is closed, the connection between the real and virtual machines break
open and view this service sshd when the service state
after opening the sshd service real machine and the virtual machine can ssh
View sshd service status at this time and the process ID of
the service after the restart process will change the number of services
will not change with the refresh process ID after reload service configuration
settings ssh service Power shut down
the sshd service is shut down and view the status
set to open services and open the boot sshd service
is set to run system-level graphical network model is no
command init 5can manually turn the graphics mode temporarily
set the system to run level graphics mode network
