Several Linux commands to work with

Recently, because of work needs, new learning a few Linux commands, record. Content Reference Related Blogs

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Iostat: Activity for monitoring disks

Command format: iostat [parameter] [TIME] [times]

With Iostat, it is convenient to view the activity of CPU, network card, TTY device, disk, CD-ROM and so on, load information

• -C Display of CPU usage
• -D Display disk usage
• -K displays in kilobytes
• -m displays in units of M.
• -N Display of disk array (LVM) information
• -N Display of NFS usage
• -p[disk] Displays disk and partition conditions
• -t display terminal and CPU information
• -X to display detailed information
• -V Display version information

Iostat Show all load conditions

CPU Properties:

%user:cpu percentage of time in user mode

%nice:cpu percentage of time in user mode with nice value

%system:cpu percentage of time in System mode

%iowait:cpu the percentage of time to wait for the input output to finish

%steal: The percentage of the virtual CPU's unconscious wait time when the hypervisor maintains a second virtual processor

%IDLE:CPU Idle time percentage

if the value of%iowait is too high, indicating that the hard disk has an I/O bottleneck, if the%idle value is high but the system responds slowly, it is possible that the CPU waits for the allocated memory, which should increase the memory capacity. If the%idle value continues below 10, the system's CPU processing power is relatively low, indicating that the most resource to be addressed in the system is the CPU.

Disk Properties:

RRQM/S: The number of requests per second that need to be read

WRQM/S: Number of required write requests per second

R/S: Number of Read I/O devices completed per second. namely RIO/S

W/S: Number of write I/O devices completed per second. namely WIO/S

RSEC/S: Number of Read sectors per second. namely RSECT/S

WSEC/S: Number of Write sectors per second. namely WSECT/S

rkb/s: Reads K bytes per second. is half the rsect/s because the size of each sector is 512 bytes.

wkb/s: Writes K bytes per second. is half the wsect/s.

Avgrq-sz: The average data size (sector) per device I/O operation.

Avgqu-sz: Average I/O queue length.

Await: The average wait time (in milliseconds) for each device I/O operation.

SVCTM: The average service time (in milliseconds) per device I/O operation.

%util: How much time in a second is spent on I/O operations, which is the percentage of CPU consumed by IO

if%util is close to 100%, it indicates that there are too many I/O requests, the I/O system is full , and the disk may have bottlenecks. If the SVCTM is closer to await, it indicates that I/O has almost no wait time, and if the await is much larger than SVCTM, indicating that the I/O queue is too long and the IO response is too slow , the necessary optimizations are required. If the Avgqu-sz is larger, it also indicates that there is an equivalent IO waiting.

Common Iostat-x/dev/sda1 1 100 (refresh every 1s, refresh 100 times) to see the details of disk I/O

The SAR command is a Linux system profiling tool that analyzes file reads and writes , usage of system calls, disk I/O, CPU efficiency, memory usage, process activity, and IPC-related activities, among other things.

Command format

SAR [Options] [-A] [-o file] t [n]

which

T is the sampling interval, n is the number of samples, the default value is 1;

-o file means that the command result is stored in a binary format in a file, and file is a filename.

Options is a command-line option, and the SAR command is commonly used as follows:

-A: Sum of all reports

-P: Set CPU

-U: Output statistics about CPU usage

-V: Output statistics for inode, files, and other kernel tables

-D: Output activity information for each block device

-N: Reporting Network conditions

-Q: Report Queue length and payload information

-r: Output memory and swap space statistics

-B: Display statistics for I/O and transfer rates

-A: File read and write status

-C: Output process statistics, number of processes created per second

-r: Output memory page statistics

-Y: terminal equipment activity situation

-W: Output system Exchange activity information

Monitoring of the CPU

Sar-u-O cpuinfo 1 5 (interval 1s, sampled 5 times)

Monitoring of IO and transfer rates

Sar-b 1 5

TPS: Total I/O transfers per second of disk

Rtps: Total amount of data read from disk per second

Wtps: Total amount of data written to disk per second

BREAD/S: Amount of data read from disk per second in block/s

BWRTN/S: Amount of data written to disk per second in blocks/s

Suspected CPU bottlenecks, sar-u and sar-q can be used to view

Suspect memory bottlenecks and can be viewed with Sar-b, sar-r, sar-w, etc.

Suspected I/O bottlenecks and can be viewed with Sar-b, sar-u, sar-d, etc.

SED command: An online editor that operates on a single line of commands, primarily for editing one or more files.

sed [-NEFR] [action] options and Parameters:-N: Use Quiet (silent) mode. In the usage of general sed, all data from STDIN is generally listed on the terminal. However, if you add the-n parameter, only the line (or action) that is specially processed by SED is listed. -E: The action edit of SED directly in the command-line mode;-F: The action of SED is written in a file directly, and-f filename can run the SED action within filename; The-r:sed action supports the syntax of the extended formal notation. (The default is the basic formal notation of French)-I: Directly modifies the contents of the read file, not the output to the terminal.

Action Description: [N1[,n2]]functionn1, N2: Not necessarily exist, generally represents "select the number of lines of action", for example, if my action is required between 10 to 20 rows, then "10,20[Action Behavior" "FUNCTION:A: New, the back of a The strings can be connected, and the strings will appear on a new line (the current next line) ~c: Replace, C can be followed by a string, these strings can replace the line between N1,N2! D: Delete, because it is deleted, so d usually do not take any knock; I: Insert, I can be followed by a string, and these strings will appear on a new line (the current line); P: Print, that is, print out a selected data. Normally p will run with parameter sed-n ~s: Replace, can be directly replaced by work! Usually this s action can be paired with formal notation! For example 1,20s/old/new/g is!

The use of SED commands is often used in conjunction with regular expressions.
The main use of the SED command to modify a file in a row of content
Sed-i "s/^xxx.*$/yyyy/g" file  name  (modified to yyyy with XXX line included)

Several Linux commands to work with