Shulou(Shulou.com)06/03 Report--

1. The system clock automatically synchronizes to the NTP server

Use timedatectl to synchronize the system clock: # timedatectl set-ntp true

If NTP is installed on the system, check whether the NTP-related package is installed: # rpm-qa | grep ntp

To check the status of the service, use # timedatectl status

View all available time zones: # timedatectl list-timezones

Set local time zone (for example, Asia/Shanghai): # timedatectl set-timezone "Asia/Shanghai"

Set time and date: # timedatectl set-time "18:50:21 2019-11-05"

Setting time: # timedatectl set-time 18:50:21

Set date: # timedatectl set-time 20191105

two。 Modify hostname

Temporary modification: # sudo hostname new hostname

Permanent modification: # sudo hostnamectl set-hostname new hostname

View hostname: hostname or hostnamectl

View FQDN name: hostname-f

Check the host IP address: hostname-I

3. View processes and ports

View the sshd process: # ps-ef | grep sshd

View sshd port: # netstat-lntup | grep ssh

Or # ss | grep ssh

4. Mount the file system

View the mounted disk: # df-h

View block device information: # lsblk

Take the attached USB disk as an example: before inserting the USB disk, you should use fdisk-l or more / proc/partitions to check the hard disk and hard disk partition of the system.

Create mount point: # mkdir-p / mnt/usb

Mount usb (take disk partition sdd1 as an example): # monut / dev/sdd1 / mnt/usb

Read-only mode mount: # monut-o ro / dev/sdd1 / mnt/usb

View file contents: # ll / mnt/usb

Unmount the file system (to exit the mount directory first): # umonut / mnt/usb

If you want to automatically mount a device on boot, just modify the / etc/fstab file.

For example, if you want to automatically mount the hardware device / dev/sdb2 whose file system is ext4 to the / backup directory after boot, and maintain the default permissions without post, you need to modify the / etc/fstab file to write:

5. Installation of software

a. Source code package (usually put the source code in the / usr/local/src directory)

Decompress the source code package: # tar-zxvf * .tar.gz

Then switch to the source folder in the following order: configure-compile-install

Configure and specify the installation directory (here take ucurses as an example): #. / configure-- prefix=/usr/local/ncurses

Compile: # make

Installation: # make install

b. Binary packet mode (rpm)

Query an installed software: # rpm-qa | grep keyword

Uninstall the software: # rpm-e keyword [--nodeps]

Installation software: # rpm-ivh full name

Upgrade software: # rpm-Uvh full name

Query software: # rpm-qf file path [query which package the specified file belongs to]

C.yum installation

List currently installed and installable software: # yum list [installed]

Search for packages for specified keywords: # yum search keywords

Install the specified package: # yum [- y] install package name

Update the specified package. If you do not specify the package, update all software: # yum [- y] update package name

Uninstall the specified package: # yum [- y] remove package name

6. View system information

Processor Architecture of uname-m display Machine

Uname-r shows the kernel version in use

Cat / proc/version shows detailed kernel version or uname-a

Cat / proc/meminfo verifies memory usage

Cat / proc/cpuinfo view CPU information

Cat / proc/swaps shows which swap is used

Date displays the system time and date

Free-m to view memory usage and swap area usage

Df-h to view the usage of each partition

Fdisk-l view all partitions

Systemctl list-unit-files lists all system services

Ifconfig views the properties of all network interfaces

Iptables-L View Firewall Settings

Route-n View routing tabl

Netstat-lntp view all listening ports

Netstat-antp to view all established connections

Netstat-s View Network Statistics process

Ps-ef to view all processes

Top displays process status users in real time

W View active users

Id to view specified user information

Last views user login log

Cut-d:-F1 / etc/passwd view all users of the system

Cut-d:-F1 / etc/group View all groups of the system

Crontab-l view the current user's scheduled task service

View memory size: cat / proc/meminfo | grep MemTotal

View hard disk size: fdisk-l | grep Disk

View memory usage and swap usage: free-m

7. User management (executed under root authority)

Useradd user1 creates a new user

Useradd-c "remarks"-g admin-d / home/user1-s / bin/bash user1 create a user belonging to the "admin" user group and specify the home directory and shell

Userdel-r user1 deletes a user (- r and deletes the user's home directory)

Usermod-c "remarks"-g system-d / ftp/user1-s / bin/nologin user1 modify user attributes

Passwd modifies the current user password

Passwd user1 modifies the specified user password

Groupadd group_name create a new user group

Groupdel group_name deletes a user group

Groupmod-n new_group_name old_group_name rename a user group

8. File rights management (only for root users or file owners)

Ll or ls-l displays file permissions

Ls-m horizontal output file list

Chmod-R ugo+rwx directory1 sets permissions for directory owners (u), groups (g), and others (o) to read (r), write (w), and execute (x)

Chmod-R go-rwx directory1 deletes group (g) and others (o) read and write permissions to the directory

Chown user1 file1 changes the owner property of a file

Chown user1:group1 file1 changes the owner and group properties of a file

Chown-R user1 directory1 changes the owner properties of a directory and simultaneously changes the properties of all files in the directory

Chgrp group1 file1 changes the group of files

Chgrp-R group1 / usr/dir changes the user group of all files in / usr/dir and its subdirectories to group1

The scope of permissions is expressed as follows:

U User, the owner of a file or directory

G Group, the group to which the file or directory belongs

O Other, except for the owner of the file or directory or the group to which it belongs, all users fall within this scope

An All, that is, all users, including owners, groups, and other users

R read permission, numeric code "4"

W write permission, numeric code "2"

X execute or switch permissions, numeric code "1"

-without any permission, the number code is "0"

S Special function description: change the permissions of a file or directory.

Note: in Linux, if you want to delete a file, it is not to see whether the file has the corresponding permissions, but to see whether the directory where the file is located has write permission, and if so, you can delete it.

9. File search

1) find is used to find files in the specified directory (it takes up a lot of resources, so the search scope should be reduced as much as possible)

Search by file name:

Find / etc-name init accurate search, must be init to search

Find / etc-iname init must be init or can be searched with uppercase letters

Find / etc-name * init fuzzy search, file or directory name ending with init

Find / etc-name init??? Fuzzy search? Represents a single character

Look up according to the file type: F for file, d for directory, l for soft link

Find / home-type d find the file type in the / home directory is directory

2) locate is used to find documents in the document database

To create a new document, you need to command updatedb to update the database manually to find it with locate. In addition, the / tmp directory does not fall within the scope of the document database.

Locate-I case-insensitive search

3) which is used to search the directory and alias information where the command is located.

Which [command]

For example: which grep

4) whereis is used to search the directory where the command is located and the path of the help document

Whereis [command]

For example: whereis ls

5) grep is used to search the file for lines that match the string and output

Grep keyword file path

-I is not case sensitive

-v reverse search, that is, excluding the specified string

-m displays only the columns that match the whole word, that is, precise search

For example: grep mysql / root/install.log

10. View the contents of the file

Cat file1 forward view the contents of the file

Tac file1 reverse views the contents of the file

More file1 looks at the contents of a long file

Less file1 is similar to more, except that it allows users to browse files forward or backward.

Head-N2 file1 looks at the first two lines of a file,-n can be omitted

Tail-2 file1 looks at the last two lines of a file

Tail-f / var/log/messages view what has been added to a file in real time

11. Text processing

1) cut column interception tool. Used for column interception

-c to segment and intercept characters

Example: cut-C1-5 passwd intercepts the first to fifth characters.

Cut-c10-passwd intercepts all from the tenth character

-d custom delimiter, default to tab\ t

-f is used with-d to specify which area to intercept

Example: cut-d:-F1 passwd 3 passwd to split and intercept the first and third columns

2) sort compares each line of the file / text as a unit. The principle of comparison is to compare each other from the first character to the back, compare them according to the ASCII code value in turn, and finally output them in ascending order.

-t delimiter, similar to cut-d

-k N column, similar to cut-f

-o output the sort results to a file, similar to the redirect symbol >

-n is sorted by number, by default by character

-r sort in descending order. The default is ascending order.

-u removes duplicate lines, similar to uniq

-R is sorted randomly, and the result of each run is different.

For example: # sort-nrk 3-t: test.txt

3) uniq is used to remove consecutive duplicate lines

-I ignore case

-c Statistics the number of duplicate rows

-d displays only duplicate lines

4) tee is used to redirect data to a file, and on the other hand, it can also provide a copy of the redirected data as a stdin for subsequent commands. To put it simply, redirect the data to a given file and screen. Example

Ls-l | tee file.txt | less

And output file.txt content

-a use append mode when redirecting to a file

5) diff is used to compare differences between files line by line

Syntax: diff [options] File 1 File 2

-c context format display

-u merge format display

-Q or-- brief: only show the difference, not the detailed information

Note: the way diff describes the differences between the two files is to tell us how to change the first file to match the second file.

Sometimes we need to use one file as the standard to modify other files, and when there are more changes, we can do it by patching.

The first step is to find out the difference in the file and then output it to a file

# diff-uN file1 file2 > file.patch

-N means to treat a file that does not exist as an empty file

Second, patch different contents to the file

# patch file1 file.patch

Step 3, test and verify

# diff file1 file2

6) paste is used to merge multiple files in a queue.

Paste file1 file2 file3

-d Custom delimiter, default is tab

-s serial processing, non-parallel

Tip: clear the contents of the file by redirecting to empty, such as # > access.log

7) tr is used for character conversion, replacement and deletion, mainly for deleting control characters in files or for character conversion

Usage 1: the execution result of the command is handed over to tr for processing, where string1 is used for query and string2 is used for conversion processing.

# commands | tr 'string1'' string2'

Use 2:tr to deal with content from files, remember to use "

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