RHCSA3

Linux Directory structure

bin,sbin
The directory where the command is executed , Commands are actually executable files
bin All can be executed ,sbin Yes root Can be executed

boot Catalog
Where the operating system stores startup files , Loading kernel

dev command
Hardware files of the operating system
For example, disk.
sdxx vdxx

ect Catalog
Store operating system configuration files and installed third-party files
It's very important

home Catalog
Home directory
Directory of the current user , The current user can have full permissions
root The user's home directory is root

run Catalog
It can be considered as a virtual directory
Runtime content
In memory , No disk space

tmp Catalog
Temporary file directory
file 10 If you don't visit it for days, it will be deleted

usr Catalog
Is a static directory

var Catalog
Is a dynamic directory ,log It's just var Next

Relative path and absolute path
Absolute path ： Path starting with root
Relative paths ： A path that does not start with the root directory

pwd Print current working directory

./ Represents the current directory
…/ Indicates the parent directory

cd Toggle directory （ Home catalog ）
cd / Switch back to the parent directory

Use touch,cp,mv,rm Management document
touch Create a file
touch a b c

mkdir Create directory
-p Multilevel creation mkdir -p /aaa/bbb/ccc

cp Copy
cp Source The goal is
There can be multiple sources , There can only be one goal

mv Moving files
mv Source The goal is
You can change your name mv a b
There can be multiple sources , There can only be one goal

rm Delete file
root use rm There will be hints. , It can be used rm -rf
rm a b c To delete multiple
-r Can be used to delete directories
-f force delete
rm -rf / ( Do not use )

rmdir Delete empty directory , Cannot be used to delete non empty directories

Hard link and soft link
ln Connection command
-s Create a soft connection , It's like a shortcut , Delete source file , Soft connection failure
ln Source file Hard links Equivalent to replication , Delete source file , Hard links do not fail

The principle of hard link is inode File name is added in ,inode use ls -i see
Empathy ,linux Deleting a file is deleting inode

Source file inode Do not point to soft connection file , Redistribution inode

Use shell Expand the matching file

~ Represents the home directory of the current user
ls ~

Braces use
Usually used when creating
touch {x,y,z}
touch {1…5} establish 1-5 Of 5 File
touch file{1,2}{a,b} establish 1a,2a,1b,2b

Variable $
for example ：echo time is $(date)

Custom variable
Variable = what
echo $ Variable

notes #

ctrl+l Clear the screen