Linux operation and Maintenance

1. View the system kernel version

$Cat /etc/6.2  (Santiago) Kernel \ r on an \m

Displays the system name (Red Hat Enterprise) and the kernel version (Release 6.2)

The file/etc/issue is a text file which contains a message or system identification to be printed before the login prompt .

2. View System Information

uname -3.19. 0--generic # ~14.04. 1  - £ ºi686 i686 i686 gnu/linux

Uname-a: Displays the system name, the node name, the operating system's release number, the operating system version, the machine ID number of the running system

3. View disk space usage

$DF -hlfilesystem            Size  used Availuse% mountedon/dev/xvda1            100G  5 . 0G   90G   6/tmpfs                 1. 9G  104K  1. 9G   1%/DEV/SHM

Parameters:

• -H: Easy to read
• -A: List of all file systems

4. View Memory

A. Free command

 free-m             total       used       free     shared    buffers     Cachedmem:           3072       2459        612          0         207        1803-/+ Buffers/cache:        447       2624Swap:         1913           0       1913

Line 2nd:

Total Memory: 3072 "Note the unit is m, you can use the parameter-hm more prominent"
Used number of memory used: 2459
Free Memory Number: 612
GKFX is currently obsolete. No, always 0.
Buffers:buffer Cache Memory: 207
Cached:page Cache Memory: 2803

Relationship: total = used + Free

Line 3rd:
The meaning of-/+ Buffers/cache:
-buffers/cache Memory: 447 (equals 1th row of used-buffers-cached)
+buffers/cache Memory: 2624 (equals 1th line of Free + buffers + cached)
Note: The amount of memory here is a little bit out of size after calculating it with the above formula (you don't know what the reason is).

The visible-buffers/cache reflects the memory that is actually eaten by the program, and +buffers/cache reflects the total amount of memory that can be appropriated.

5. View the number of CPU cores

# total number of cores =Number of physical CPUs × number of cores per physical CPU # Total Logical CPUs=Number of physical CPUs x number of cores per physical CPU X number of hyper-threads # View the number of physical CPUsCat/proc/cpuinfo|grep "Physical ID"|Sort|Uniq|WC-l# View the number of cores in each physical CPU (that is, the number of nuclei)Cat/proc/cpuinfo|grep "CPU Cores"|Uniq# View the number of logical CPUsCat/proc/cpuinfo|grep "Processor"|WC-L

6. View System Load

Uptime at:min,  2 users,  0.080.03 0.05

• Current Time 15:41:09
• Time the system has been running 42min
• Current users online 2 user
• Average load: 0.54, 0.40, 0.20, last 1 minutes, 5 minutes, 15 minutes system load

What is the system load?
The average system load is defined as the number of average processes running in a queue during a specific time interval . If a process meets the following criteria, it will be in the run queue:

• It is not waiting for the results of the I/O operation
• It does not actively enter the waiting state (that is, "Wait" is not called)
• Not stopped (ex: waiting to be terminated)

In general, the current number of active processes per CPU core is not greater than 3, the system performance is good! Of course, it is said that each CPU core, that is, if the host is a quad-core CPU, then as long as the uptime the last output of a string of characters less than 12 means that the system load is not very serious. Of course, if you reach 20, it means that the current system load is very serious and it is very slow to open the execution web script

Linux operation and Maintenance