Linux preparation stage

 

Author: graynight

Basic course 1-shell text processing tool

Bash shell

* Matches zero or multiple characters.

? Match any single character

History and Tab play the same role in vro switches.

How to return to the main directory: 1.cd 2.cd/root 3/cd ~

Text processing tool:

 

 

Less and cat. Use cat to fill the screen with content in an instant. You can use less to present the content one by one and exit with the Q key.

Head-n indicates the first n rows

Tail-n displays the last n rows of the file

Grep extracts keywords from the file, which is equivalent to searching ).

Wc word count: calculates the total number of words, the total number of rows, the total number of bytes, and the total number of characters.

-I: calculates the number of rows only.

-W: calculate the total number of words only

-C: calculates the total number of bytes.

Tr converts the characters in a set into the corresponding characters in another set.

Data Display date

Cal display calendar

A simple description of the whatis command

Makewhatis generate Database

Help Show help

Man displays the command manual, the up and down keys on the keyboard flip pages, q key exit

Info displays more details than man

Important directories:

Main Directory:/root (System Administrator)

/Home/User Name (normal user)

User executable file directory:/bin/usr/bin/user/local/bin

System executable file directory:/sbin/usr/local/sbin

Other mount points:/media/mnt

Configuration:/etc

Temporary File:/tmp

Kernel and boot Loader:/boot

Server data:/var/srv

System Information:/proc/sys

Shared Library:/lib/usr/local/lib

Touch creates an empty file or updates the file Timestamp

The pre-built file database on the locate query system may only search for directories with read and execution Permissions

-I: perform case-sensitive searches.

-N X lists only the first X matching items.

The find directory condition is slower than the locate command but more accurate than the locate command. If no directory is specified, the current directory is used. If no conditions are specified, all files are matched. You can execute commands on the files you find. You may only search for directories with read and execution permissions.

You can use the OK and-exec options to run commands on the found files. If you use the OK option, a confirmation prompt will be prompted before running each matching file. If you use-exec, the command will not allow you to confirm all matching files in the second team.

The find condition accepts numeric values as parameters.

Find-size + 1024 K greater than 1024 K

Find-size-1024 K less than 1024 K

The find command can be matched according to the timestamp.

-The atime file was last read.

-The last time the mtime file was changed

-The data in the ctime file or the original data was last changed

Find-ctime-10 file modification date less than 10 days

TCP/IP network configuration

Nic interfaces use continuous numbers such as eth0 eth1

View ifconfig commands

Use ifup to enable the interface

Use ifdown to disable the interface

You can also use a graphical interface for management.

The device configuration is saved in the text file/etc/sysconfig/network-scripts/ifcfg-ethX

Other global network settings/etc/sysconfig/network

DNS configuration/etc/resolv. conf

Use ps to view process information. By default, processes on the current terminal are displayed.

-Option a includes processes on all terminals

-The x option includes processes that do not connect to the terminal.

-U option includes the process owner information

-O property options display custom information

Ps axo comm. pid. user | grep XXX

Search for pidof by exact program name

Signal: the most basic communication mode between processes. It is a simple message that can communicate with processes using commands such as kill.

Send kill signal pid to process

The name or number of the sent signal can be used.

Signal 15 term (default) Clean termination

Signal 9 kill immediate termination

Signal 1 hup re-reading configuration file

Killed 3428

Kill-15 3428

Scheduling priority: the scheduling priority determines the CPU usage, and the priority is affected by the process's "Good Intentions. The value range is-20 to 19. The smaller the default value, the higher the CPU usage priority. Run the ps-o comm and nice commands to view the value.

Change the scheduling priority: when the process is started: nice-n 5 command. After startup: renice 5 pid.

Normal users cannot set the nice value to a number smaller than 0, only the root user can

Top interactive process management tool: displays a list of processes running on your system on the screen, updated every 5 seconds.

Configure the IP address of the NIC: Dynamic (DHCP): dhclient eth0 static: ifconfig xx. xx

DNS Client configuration: edit/etc/resolv. conf to add nameserver xx. If multiple nameservers are specified, the system will retrieve servers in order.

Default GATEWAY: define global default GATEWAY = xx in/etc/sysconfig/network. xx. xx. xx you can also define the default GATEWAY of a network device in the ifcfg file under/etc/sysconfig/network-scripts/to automatically overwrite the configured GATEWAY in the ifcfg file. xx. xx. xx

File compression

Some common compressed file extensions

*. Z compress compressed files

*. Bz2 bzip2 files compressed by the program

*. Gz gzip compressed files

* The data packaged by the. tar program is not compressed.

* .Tar.gz tar files are compressed by gzip.

Compress-d [file name]-d is the decompression parameter. If you use the original compress file, it will be replaced by the compressed file.

Bzip2 [-dz] File Name-d decompression-z compression bzcat file name .bz2 read compressed file content

Gzip [-d #] File Name-d decompression # compression level 1 is the worst, 9 is the best, 6 by default, zcat file name reads compressed file content level is lower the faster

Tar [Option] File Name

-Whether z has both gzip

-X unzipping a compressed file

-T view the files in the tarfile

-C. Create a compressed file

-V display files during compression

-F use the file name

-P: use the original attribute of the source file.

-P can use absolute paths.

-N is a new file than the subsequent date (XXXX/XX) to be packaged.

Hardware and system logs

Access the driver through/dev, and files in the/dev directory can be used to access the driver.

Read data from the serial port: cat/dev/ttyS0

Write Data from the serial port: echo "data">/dev/ttyS0

Ls-l/dev/ttyS0 serial port device

Ls-l/dev/sda1 USB device

/Dev/hda/dev/hdc IDE Hard Drive

/Dev/sda/dev/sdb scsi sata or USB storage device

/Dev/md0/dev/md1 software RAID

/Dev/tty0-6 virtual console

/Dev/null/dev/zero software device

/Dev/random/dev/urandom: random Number

Who I am viewing Terminal

Hal-device lists snapshots of all connected devices in text mode. hal management is available (hardware extraction layer)

Lspci and susb respectively list the devices connected to the pci and usb Bus

Log daemon: syslog klogd

Log File:

/Var/log/dmesg kernel boot program

/Var/log/messages standard system error information

/Var/log/maillog email system information

/Var/log/secure security authentication information

User Management

Add new user: useradd

Set Password: passwd account name

Add a group account: newusers

When a user account is created, a dedicated group user with the same name is also created and assigned to this dedicated group.

Group Management

You can use the groupadd command to create a new group.

Use the groupdel command to delete a group

Use groupmod to change the name

Use the chage username option to change the password validity period, or use the option-m Password Change shortest interval-M Password Change shortest interval-E password failure on this day

Su-user Account change

User

1. Each user is assigned a unique user ID (UID)

2. the user name is saved in the/etc/passwd file.

3. When users log on, they are allocated a home directory and a running program.

Group

1. All users belong to a group

2. Each group is assigned a unique group ID (GID) stored in/etc/group.

3. All users in the group can share files belonging to the group.

Priority of Permissions

1. If the UID is assigned, apply the user permission

2. Otherwise, if the GID matches, the Group permission is applied.

3. If none of them match, apply other permissions.

Linux file access permission type

1. UID permission

2. GID permission

3. Other QIT Permissions

Permission type

1. r. Read the file or list the contents of the directory.

2. w. Write the file, or create or delete the file in the directory.

3. x execute the program or transfer it to the directory

4.-: no permission

Change file owner

1. Only the root user can change the file owner.

2. Only the root user can change the file group.

3. The chown command is used to change the user

4. The chgrp command is used to change the group

Change File permissions-symbolic Method

Chmod files

The mode here is: u g or o represents the user group and other users + or-represents granting or rejecting r w x represents reading, writing, and executing respectively.

Number: 4. Indicates reading 2. Indicates writing 1. Indicates executing 0. Indicates canceling all permissions.