Process Management for Linux operating systems

Tutorial: Linux Process Management is much more powerful than Windows, and all processes are mapped to the/proc directory, we can view the memory data of these processes as we operate on common files.

~ $ Ls-l/proc

Dr-xr-x 7 root 0 1
......
-R -- 1 root 0 version
-R -- 1 root 0 version_signature
-R -------- 1 root 0 vmallocinfo
-R -- 1 root 0 vmstat
-R -- 1 root 0 zoneinfo

~ $ Cat/proc/version
Linux version 2.6.28-11-generic (buildd @ palmer) (gcc version 4.3.3 (Ubuntu 4.3.3-5ubuntu4) # 42-Ubuntu SMP Fri Apr 17 01:57:59 UTC 2009

1. Job Management

Use "&" to place commands in "background" for execution

~ $ Nano a.txt & # Run the nano editor in the background

[1] 12988

[1] + Stopped nano a.txt

~ $ Jobs # view all currently executed jobs

[1] + Stopped nano a.txt

~ $ Fg 1 # transfer 1 job to the foreground for execution

Press Ctrl + Z to save the program being executed to the background. For background programs in the "Stopped" status, we can use "bg" to make them "Running" in the background ".

~ $ Sleep 1 m # sleep for 1 minute, and press Ctrl + Z to run it in the background.

^ Z
[1] + Stopped sleep 1 m

~ $ Jobs

[1] + Stopped sleep 1 m # The sleep command is "suspended ".

~ $ Bg 1 # Use fg to run sleep in the background.

[1] + sleep 1 m &

~ $ Jobs

[1] + Running sleep 1 m &

We can use the "kill" command to terminate the job.

~ $ Jobs

[1] + Stopped sleep 1 m

~ $ Kill-9% 1

[1] + Stopped sleep 1 m

~ $ Jobs

[1] + Killed sleep 1 m

Kill has several main parameters:-1 reload;-2 Ctrl + C;-9 Force Delete;-15 exit in normal mode.

2. Process Management

"Ps" is used to view the currently running process. There are many parameters, but "aux" is commonly used ".

~ $ Ps aux | more

User pid % CPU % MEM VSZ RSS TTY STAT START TIME COMMAND
Root 1 0.0 0.3 3084 1884? Ss/sbin/init
Root 2 0.0 0.0 0 0? S <[kthreadd]
Root 3 0.0 0.0 0 0? S <08:00 0: 00 [migration/0]
Root 4 0.0 0.0 0 0? S <08:00 [ksoftirqd/0]
Root 5 0.0 0.0 0 0? S <08:00 [watchdog/0]
Root 6 0.0 0.0 0 0? S <08:00 0: 00 [events/0]
Root 7 0.0 0.0 0 0? S <[khelper]
Root 8 0.0 0.0 0 0? S <08:00 0: 00 [kstop/0]
Root 9 0.0 0.0 0 0? S <08:00 0: 00 [kintegrityd/0]
Root 10 0.0 0.0 0 0? S <[kblockd/0]
Root 11 0.0 0.0 0 0? S <[kacpid]
Root 12 0.0 0.0 0 0? S <08:00 [kacpi_notify]
...

Display result column:
USER: USER Account
PID: process ID
% CPU: CPU usage percentage
% MEM: memory usage percentage
VSZ: virtual memory usage
RSS: Fixed memory usage
TTY: Terminal
STAT: running status (R: running; S: sleep; T: terminated; Z: botnets for some reason)
START: START Time
TIME: CPU running TIME
COMMAND: COMMAND Line
We can also directly view a single process.

~ $ Ps 34

PID TTY STAT TIME COMMAND
34? S <0: 00 [kmpath_handlerd]

~ $ Ps-C ksnapd

PID TTY TIME CMD
35? 00:00:00 ksnapd

Unlike static ps output, "top" can dynamically refresh process information (the default interval is 5 seconds ).

~ $ Top

Top-12:02:29 up, 2 users, load average: 0.04, 0.04, 0.01
Task: 113 total, 1 running, 111 sleeping, 0 stopped, 1 zombie
Cpu (s): 0.2% us, 1.3% sy, 0.2% ni, 97.6% id, 0.6% wa, 0.0% hi, 0.0% si, 0.0% st
Mem: 509504 k total, 436672 k used, 72832 k free, 79376 k buffers
Swap: 409616 k total, 0 k used, 409616 k free, 212208 k cached

Pid user pr ni virt res shr s % CPU % mem time + COMMAND
14 root 15-5 0 0 S 1.9 0.0. 08 ata/0
1 root 20 0 3084 1884 S 564 0.0. 43 init
2 root 15-5 0 0 S 0.0 0.0. 00 kthreadd
3 root RT-5 0 0 S 0.0 0.0. 00 migration/0
4 root 15-5 0 0 S 0.0 0.0. 33 ksoftirqd/0
5 root RT-5 0 0 S 0.0 0.0. 00 watchdog/0

Line 1: system startup time; number of online users; system load for 1, 5, and 10 minutes (generally no more than 1. Check if the duration is greater than 5 ).
Row 2: Process statistics. Zombie indicates the number of zombie processes.
Row 3: CPU load statistics.
Row 4: memory usage statistics.
Row 5: virtual memory usage statistics.

Process column information:
PID: process ID
USER: USER Account
PR: Priority (Execution earlier and earlier)
NI: Nice
% CPU: CPU usage percentage
% MEM: memory usage percentage
TIME +: CPU running TIME
COMMAND: COMMAND Line
We can use the "-d" parameter to specify the refresh frequency (in seconds)

~ $ Top-d 1

The "-p" parameter is used to specify a specific process number.

~ $ Top-d 1-p 13952

During running, you can press "h" to enter the Help menu and view shortcut keys such as display and sorting.

3. Process Priority

Each process has a "Priority" attribute, and the system arranges the execution order by Priority (ascending.

PRI (new) = PRI (old) + Nice

Since PRI is determined by the system "dynamic", we need to adjust the priority through Nice.

~ $ Nano &

[1] 15174

[1] + Stopped nano

~ $ Ps-l

F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
0 R 1000 15086 15082 0 80 0-1447-pts/0 00:00:00 bash
0 T 1000 15174 15086 0 80 0-929 signal pts/0 00:00:00 nano
0 R 1000 15177 15086 0 80 0-635-pts/0 00:00:00 ps

~ $ Sudo renice-5 15174 # adjust priority

15174: old priority 0, new priority-5

~ $ Ps-l
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
0 R 1000 15086 15082 0 80 0-1447-pts/0 00:00:00 bash
0 T 1000 15174 15086 0 75-5-929 signal pts/0 00:00:00 nano
0 R 1000 15182 15086 0 80 0-635-pts/0 00:00:00 ps