0. Description
From Tencent video Linux development video, mainly for my own review
Linux 1. Overview
1.1 origin and development of Linux
unix is a time-sharing operating system (the difference between time-sharing system and real-time system) https://blog.csdn.net/WZJwzj123456/article/details/83243453 )
GNU(GNU is not Unix) aims to eliminate restrictions on software copying, distribution and modification
GPL (GNU General Public License) guarantees the freedom of GNU software to all users through the agreement
LGPL is more business friendly than GPL
BSD(Berkeley Software Distribution)license
Copyright and copyleft, the former is copyright, the latter is free and free
What is the difference between Linux kernel and distribution?
The distribution has more applications, and the kernel is the core program.
Extended reading: https://baijiahao.baidu.com/s?id=1603028095502634219&wfr=spider&for=pc
1.2 structure and file system type of Linux
kernel: the following is the hardware. There are hardware drivers and system management
Runtime: rich library, system application
shell: user interaction, command line
Utilities: Applications
EXT3 and EXT4 are the default file system types of Linux
FAT32 and NT
SWAP type file systems are only used in Linux SWAP partitions
The principle of swap in Linux. The size of swap is generally twice that of memory
1.3 file attributes and directory structure of Linux
FHS(Filesystem Hierarchy standard)
Differences between / bin and / usr Blogs: https://www.cnblogs.com/fengjunhua/p/7737607.html
/sbin: executable that requires special permissions
/etc: configuration file, host name, network card address. It can be saved after shutdown
/var: put frequently changing data, such as logs and emails
/proc: virtual directory. After shutdown, there is no content. The port mapped in. Operating system kernel information.
/sys: virtual directory
/opt: third party software
/mnt: manual mount directory
1.3 installation of Linux system environment
The number of main partitions plus expansion partitions shall not exceed 4, the maximum number of main partitions shall not exceed 4, and the expansion partition shall not exceed 1. The logical partition is in the expansion partition (there is no limit on the number of logical partitions). Generally, partitions are formatted, and blank partitions are not formatted.
Difference between primary partition and extended partition:
1. Main partition
The primary partition is also called the boot partition. Windows system generally needs to be installed in this primary partition, so as to ensure automatic entry into the system after startup. In short, the primary partition is a disk partition that can boot the computer to read files,
A hard disk can create up to four primary partitions at the same time. After creating four primary partitions, you can no longer create extended partitions and logical partitions. In addition, the primary partition is independent, corresponding to the first partition on the disk. At present, most computers generally divide Disk C into primary partitions when partitioning.
2. Extended partition
Extended partition is a concept, which can't be seen in the hard disk and can't be used directly.
In addition to the primary partition, the remaining disk space is the extended partition. When a hard disk allocates all capacity to the primary partition, there is no expansion partition. Only when the capacity of the primary partition is less than the capacity of the hard disk, the remaining space belongs to the expansion partition. The expansion partition can continue to be expanded and divided into multiple logical partitions.
3. Logical partition: the extended partition cannot be used directly. It is used in the way of logical partition, so the extended partition can be divided into several logical partitions. Their relationship is an inclusive relationship, and all logical partitions are part of the extended partition. If the extended partition is no longer partitioned, the entire extended partition is a logical partition.
1.4 installation of Linux system environment
Virtual machine installation, 1 / 4 of the real memory, the cpu has several cores to write
Install using ISO image files
Recommendation: during installation, press F2 to cut off the BIOS interface immediately after restart. Use the + button in Boot to put the CD-ROM on the top and start from the CD-ROM to avoid starting from VMware Player. Then press F10 to save exit
After installation and shutdown, prompt to remove the disc. Do not check the link at startup in the equipment status.
2. Command overview
2.1 command format and help
Ordinary users are $, privileged users are $#
type pwd type ls
Find commands in vim
# Look from top to bottom /Find content # Look from bottom to top ?Find content
3. Directory operation
3.1 path concept of directory
Relative path and absolute path
3.2 directory operation
# Lists the self information of the current entry ls -d # Create multi-level directories recursively mkdir -p # Directory copy command cp -a # Copy all cp -f # A forced copy, overwrite existing # remove empty directories rmdir -p # Recursively delete multiple empty directories # Delete non empty directory rm -i# interactive # Directory move rename mv
4. File operation
4.1 document display and filtering
# In a terminal while :;do echo "hello LiLi." >> test.txt;sleep 1; done # In another terminal tail -f test.txt # This is often the case when viewing log files
4.2 addition, deletion and copy of documents
# In the root directory, find the file with cc in the file name, and start from below the root directory find / -name "cc" # You can only find the executable file and find it in the PATH variable which cc #which can only find the executable file and find it in the PATH variable. #whereis looks from the linux file database (/ var/lib/slocate/slocate.db), so it is possible to find the newly deleted or newly created file. Match all #locate is the same as above, but the file name is a partial match. #find is a direct search on the hard disk. It has powerful functions, but it consumes the hard disk and is generally not used. # locate uses index technology to find locate cc
4.3 basic editing of text editor
vim--->After entering directly :q--->You can't exit directly :w File name--->Save exit # copy yy # Paste, paste lowercase below the current line, and paste uppercase above the current line p,P # Add line o,O # Delete line dd # You can add numbers in front of commands # /Search down? Yes, look up # : s replaces the current line, g is global (all of the current line), and c is comfort :s/io/IO/gc # % s full text replacement: :%s/io/IO/gc # Last line shift+g # first line gg
vim multiline comment:
https://www.cnblogs.com/yangzp/p/10791870.html
4.4 advanced editing of text editor
# Jump to line 13 :13 # The line number is not displayed :set nonu # Line number display :set nu # Written in vimrc, the point here means to hide the file vim ~/.vimrc set nu set tabstop=4 set autoindent #Auto indent # Undo and fallback in command mode Lowercase u ctrl+r # Multiple files are executed in parallel. The advantage is that the contents of multiple files can be transferred to each other vim 1.cc 2.cc 3.cc :args#View several file parameters : first#Go to the first file : last#Go to the last file : next#Next file : prev#Previous file
5. File compression and archiving
5.1 basic file archiving and compression
5.2 7z compression and archiving
Advantages of using 7z: high compression ratio; Rar format can be decompressed, but rar cannot be compressed
. o file: target file. It is equivalent to an obj file in windows c or cpp file corresponds to one O documents
. a file::: there are many o combined static library files, equivalent to those under windows lib file. Provide interfaces to external programs for static connection, i.e. STATIC mode. Multiple A can link to generate an exe executable
. so file::: it is a shared object, that is, a dynamic link file, and windows dll file, which is used for dynamic connection. Load only when used.
. bin file::: executable file under linux, equivalent to that under windows exe file.
6. Equipment mounting, software package upgrade and installation
6.1 mount and unload concept
The computer is automatically mounted in the directory / media
Mount a file to a directory
# View disk sudo fdisk -l
What are the reading materials and equipment documents: https://blog.csdn.net/gnnulzy/article/details/85117183
6.2 mounting and unloading equipment
# iso9660 file format, / dev/cdrom is the device file, / mnt is the directory (- t can be omitted sometimes) (this is the mounting of the optical disk device) sudo mount -t iso9660 /dev/cdrom /mnt # iso is a file, not a device. Put the file in the loopback device, and then loop and mount it in / media (mount the CD image file) sudo mount -o loop -t iso9660 mycd.iso /media # Because the CD-ROM is read-only, there will be a warning after mounting, but the u-disk will not # When using - A to uninstall, it indicates that the device is busy and needs to wait for a while. It is not an error # Uninstall device and directory equivalents
6.3 software package upgrade
# Update software list sudo apt-get update # Upgrade a software sudo apt-get upgrade vim
7. Process management
7.1 process view
# $$is the current process. To view the specified process, just follow - p with the pid number top -p $$
7.2 process control
Termination is normal exit, and suspension is interrupted exit
# View process number pidof gedit
8. System management
8.1 simple system operation
Shutdown can specify a time before shutdown.
sudo is required for reboot and shutdown
8.2 planned tasks
man cront # See Chapter 5 crontab man 5 crontab # Edit crontab crontab -e # After entering the crontab, / 1 is every 1 minute, without / is the fifth minute of each time # m h dom mon dow command */1 6,8-10 * * * tar czf /home/iotek/dabao.tgz /home/iotek/*.deb # Restart cron service sudo service cron restart # View date date # Set system time sudo date -s "5:58:55" # View help documentation for crontab crontab -h # delete crontab -ri # Looking back, does crontab still exist crontab -l
8.3 memory status viewing
du -s /home/iotek du -h /home/iotek/examples.desktop
8.4 disk partition
A partition is a write to a device file
Press m to view the help file form
Press n to add the partition
p is the main partition and e is the expansion partition
Set partition number (default)
Set sector (default)
Press p to print
Extended partitions cannot be used directly and need to be divided into logical partitions
Press n
Divide the logical partition by l -
Now I don't want to change the logical partition to linux, but change this id
Finally, linux is changed to fat32
The type of all partitions can be list ed in uppercase L (hexadecimal representation)
Press p again to see that the partition type is changed, but it is not finally written into the device file. Remember to enter w!!!!
syncing synced to disks
Finally, sudo fdisk -l check it out
9. Network connection and address viewing
9.1 network connection and address viewing
# Local address link ping 127.0.0.1 # Stop after sending 6 times ping -c 6 127.0.0.1 # Domain name is OK ping www.baidu.com
ifconfig only temporarily changes the network interface address
lo is a virtual network card, local loopback, take a circle on the network protocol, and then come back
The hardware address mac address is the ID card of the network card. The ip address can be changed, but the network card address cannot be changed
9.2 domain name resolution
The web page cannot be opened, qq can log in. It indicates that the network connection is normal and the domain name resolution is faulty
Note: not all IP addresses support reverse resolution
9.3 view of routing and network statistics
#Add a gateway sudo route add default gw 192.168.248.3 # Delete gateway sudo route del default gw 192.168.248.2
# View routing table netstat -r
10. User management
10.1 user addition, deletion and viewing
# Add a user, but there is no directory and the creation is incomplete sudo useradd bencai # Delete this user sudo userdel bencai # Create a user with a directory sudo useradd -m bencai # Set password for user sudo passwd bencai # Login user su bencai whoami exit
10.2 user switching
# Ordinary users $Symbol root user#state sudo -i # Operate in the specified user sudo -u bencai ls /home # Commands that sudo can execute sudo -l # Error: user01 is not in sudoers folder sudo bencai # Exit the bencai environment and enter the root permission sudo -i # Add user01 to sudo group gpasswd -a user01 sudo # Change the ip address of lo sudo ifconfig lo 127.0.0.8
User account configuration 10.3
sudo usermod -L user01 # Failed to switch from current user to user01 su user01 # But administrators can sudo -i su user01 whoami exit passwd user01 # Unlock user sudo usermod -U user01
less /etc/passwd# System users cannot log in in the user interface. Only bencai and user01 can log in sudo less /etc/shawdow
11. User group management
11.1 adding, deleting and viewing user groups
sudo groupadd user02 tail /etc/group sudo groupdel user02 # Specify id sudo groupadd -g 1007 user02
11.2 user group account configuration
Effective group?
When groups view the user's group, it will pop up a lot. When the iotek user touch es a File file, only the iotek group can access the File. Now I want the bencai team to visit. First, there should be bencai in the group, and then turn bencai into an effective group (the first group is an effective group)
# Add user iotek to bencai sudo gpasswd -a iotek bencai # Change user bencai from last to first newgrp bencai whoami groups touch test.out # You can see test Out's group has changed ls -l # Remove user iotek from bencai
# Restrict group access sudo gpasswd -R bencai # bencai appears when viewing the file less /etc/gshadow
12. File permission attribute
12.1 concept of document authority
For the directory, the executable representative is accessible
12.2 file permission setting
# View the properties of the directory itself ls -ld newdir # In non numeric form umask -S # Ordinary files do not have executable permissions # Delete a directory rmdir
12.3 setting of document owner and group
# chown can also change the group. Only one group can be handled, so chgrp is used recursively # : users in front and groups in the back sudo chown iotek:iotek newdir sudo chown :iotek newdir
13.Linux network services
13.1 use of FTP
ftp file transfer
ftp uses the file name and login password to log in
ftp has two transmission modes, binary mode and file mode. The binary file has no format conversion, and the file loss is less
Upload to the server and download to the local
Login with account and password
ls no! Is to list the directories on the server; ls plus! Yes lists the current directory
In addition to two transmission modes, the mode of data connection: active / passive mode
Passive mode on
Active mode, the server actively connects you
In passive mode, the server is waiting for you to connect
bi is binary mode
ascii is a file schema
Upload successful
Download successful
sign out
13.2 installation of FTP service
View process number
Uninstall or use auto remove
Only ping can be installed online
The files downloaded by apt are in this path
# Offline installation sudo dpkg -i vs*.deb
13.3 startup, shutdown and configuration of FTP service
# View current status sudo service vsftpd status
anonymous_enable anonymous login
Normally open local_enable and write_ Enable (refers to the ability to upload. Otherwise, it can only be downloaded)
Welcome interface
Ensure that the newly configured file is read again, restart and reload
13.4 use of SSH
sudo apt-get install ssh
windows connection
13.5 installation, startup, shutdown and configuration of SSH service
# Installation package ls /var/cache/apt/archives/openssh*
vim /etc/ssh/sshd_config
14. Environment and functions of shell
14.1 command completion and command history
After logging in, the first execution is / bin/bash
14.2 command alias
alias type ls which ls /bin/ls alias myls='ls -ld --color=auto' myls
14.3 wildcards
ls -l test[0-9, a-z].sh ls -l test[0-2]*.???
14.4 operation control
# Background operation gedit& #[3] 28374 3 stands for job number and 28374 stands for pid # Change homework 3 back to the front desk, which is occupied by the front desk fg %3
bg will resume the background program from suspension and finish running
15.Shell variable
15.1 concept of variable and user-defined variable
Why do you sometimes add {} to a quote?
I need to speak English right away. The difference is whether it is a variable name or a variable name plus a string
15.2 environment variables of path
The host name and ip address are all in one configuration file. Read this configuration file after startup
bashrc only changes the current user
Change all etc directories
# View all environment variables env # Environment variables are saved in these two files (global) less /etc/bash.bashrc less /etc/profile # Generally, don't change the overall situation # At home less ~/.profile less ~/.bashrc # PS (Prompt Sign): command prompt PS1='\u@\w\$:' # Load modified file . ~/.bashrc # Restart start shell echo $PS1
ps related information
https://www.jianshu.com/p/d4b905e76528
# Export environment variables export PS1 # Generate sub shell bash
# The advantage of environment variables is that you don't have to add paths when running commands ls /bin/ls # Same effect cp bin/ls ils # Running ils directly failed /home/dwz/ils #Can run # Temporarily add environment variables PATH=/home/dwz/ils:$PATH
15.3 other environmental variables and predefined variables
echo $PS1 # \u Is the current user,:@Meaningless format,\$Ordinary users are $,Privileged users are# PS1='\u:@\$' sudo -i exit # PS2 is a prompt for line breaks # ls -l \ then enter and wrap
echo $$ echo $0 # Kill the current shell kill -9 $$ # echo $? # 0 is success and 1 is failure dasfhj #Random input echo $? #Return non-zero # Add & after the command to send it to the background sleep 10000& # [1] 28628 echo $! kill -9 $! # View current background tasks jobs
15.4 location variables
There are only 9 position variables in total. When it is not enough, use shift to switch
Task 1: vim test.txt \Text content ls -ld $1 ls -l $1 \ # . equivalent to source, load the file into the current shell to run . test.txt /home Task 2: vim test.txt \Text content ls -ld $1 ls -l $1 shift ls $2 \ # Pass in three addresses, exceeding the number of variables in txt. When you meet shift, automatically push back a parameter, $2 refers to / ect Finally, / home and / etc are displayed . test.txt /home /var /ect #
16. Piping and redirection
16.1 use of pipes
# grep -v contains no fields ps aux | grep "bash" | grep -v "grep" # Standard error messages are not piped # newdir is a normal file and asdhiffeljh is an error message. Finally, the error information is not filtered through the pipeline, but also directly output ls -l newdir asdhiffeljh | grep test
16.2 output redirection
Overwrite redirection is to empty the original file
Additional redirection is added at the end of the file
Default descriptor file 1
16.3 redirect and merge input
# By default, cat outputs whatever the keyboard inputs ctrl + d end cat output.txt cat < output.txt # When EOF ends, EOF can take end and BBB by itself cat << EOF > asfdjh > asfhjk > asdfhjk > EOF
# Although the error file cannot be written to output Txt file, but empty the original file ls -l djbfa/ > output.txt # Objective: to input both correct information and error information into the file # The correct information is in, but the error information is not in ls -l dfka/ /home/dwz > output.txt # The error information is in, but the correct information is not in ls -l /home/dwz dfka/ 2 > output.txt # Correct operation ls -l /home/dwz dfka/ & > output.txt
16.4 pipeline and redirection application
ls -l | grep bencai > output.txt # cat was originally output to stdin and redirected input to output2 Txt cat < output.txt > output2.txt cat > output3.txt << FF
Device files were originally stored in memory and then entered into the
17.Shell script
17.1 script programming overview
Three ways for scripts to run
By outputting the process number and process name, you can see the difference between the two different ways of running scripts,
17.2 summary of branch structure
17.3 example – branch structure
#!/bin/bash # Scheme 1: symbol cascade: test -x test2.sh && echo "ok" || echo "failure" # Scheme 2: if else branch: # There are spaces before and after [] if [ -x $1 ] then echo "ok" # Two commands in a line, with semicolons elif [ -x $2 ];then echo "$2 executable" else echo "fail" fi # Scheme 3: case branch: # Assignment = no spaces allowed Value=$3 case $Value in a) echo "A" # There are two semicolons ;; b) echo "B" ;; # *Wildcard *) echo "C" ;; esac
17.4 description of cycle structure
17.5 example – cyclic structure
#!/bin/bash Count=1 # First kind #while [ -x $1 ] # Second until [ -x $1 ] do [ $Count -ge 5] && break echo "running..." let Count++ done # Third Count=1 for Var in aa bb cc dd ee ff do echo "loop $Count" echo "$Var running..." let Count++ done
18.Shell script
18.1 example – analysis of scripts
18.2 presentation – scripting
#!/bin/bash #------------------------ #--Choose 10 multiples of 3, starting with a given natural number #------------------------ #--Input read -p "Please enter a natural number:" Input if [ $Input -gt 0] 2 > /dev/null ; then echo "You entered a natural number. The multiple of 10 3's starting from this natural number is" else echo "What you entered is not a natural number. The program exits abnormally." exit fi #--Process and output Count=0 Num=$Input while [ $Count -lt 10 ] do let Num2=$Num%3 if [ $Num2 -eq 0 ] ; then echo "$Num" let Count++ fi let Num++ done
18.3 script debugging and debugging
/Contents of dev/null: https://www.cnblogs.com/songgj/p/8998049.html
When the input is not a natural number, the error will be input into / dev/null
19. Advanced topics for shell scripts
19.1 shell functions
!!! Note: here are two $1, but the meaning is different. echo "$1 Hello" here represents the parameter "$1 Haitong", while nihao "$1 Haitong" here represents the parameter iotek input outside the file (see the figure below)
19.2 replacement of shell variables
# Delete a variable
unset today
# The variable today is empty
echo $Today
# Show friday
echo ${Today:=friday}
# Show friday
echo $Today
unset Torrow
# Default error reporting
echo ${Torrow:?"no set value"}
Torrow=sunday
# Display output sunday
echo ${Torrow:?"no set value"}
19.3 case explanation - guessing game
bug fix:
