The Ultimate Guide to Linux Commands: Become a System Operations Expert

Linux | Red Hat Certified | IT Technology | Operations Engineer

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Linux Course Notes

Directory Structure

/：Root directory, the only top-level directory

Path example: /home/itheima/a.txt indicates the a.txt file in the home/itheima folder under the root directory

Basic Commands

ls: List files

ls [options] [directory]# Options:# -l Display in list format# -h Human-readable file size (requires -l)# -a Show hidden files (files starting with `.`)

pwd: Display current working directory

pwd

cd: Change directory

cd [target directory]# If no argument is provided, switch to the user's HOME directory# Special path symbols:# ~ represents HOME directory (e.g., cd ~)# . represents the current directory# .. represents the parent directory

File Operations

mkdir: Create a folder

mkdir [-p] directory path# -p: Automatically create parent directories (preceding paths)

touch: Create a file

touch file path

cat: View file content

cat file path

more: View file in pages

more file path# Space to page down, q to exit

Copying and Moving

cp: Copy files/folders

cp [-r] source path target path# -r: Copy folder (recursively)

mv: Move/Rename

mv source path target path# If the target path does not exist, it performs a rename

Deleting and Searching

rm: Delete files/folders

rm [-rf] file or directory# -r: Delete folder# -f: Force delete (no confirmation prompt)

Warning: rm -rf / will delete all system files! Use with caution!

find: Search for files by name

find starting path -name "file name"# Supports wildcards, e.g., *test matches files ending with test

grep: Filter keywords

grep [-n] "keyword" file path# -n: Display line numbers of matching lines

Pipes and Statistics

Pipe symbol |

command1 | command2# Example: cat a.txt | grep "hello"

wc: Count file information

wc [-clmw] file path# -c: Byte count# -l: Line count# -w: Word count

Permission Management

chmod: Change permissions

chmod [-R] permission value file/directory# Permission value example: 755 (rwxr-xr-x)# -R: Recursively change all files in the directory

chown: Change owner

chown [-R] user:group file/directory# Example: chown root:root file.txt

Users and User Groups

Create User/Group

# Requires root permissionuseradd usernamegroupadd groupname

Delete User/Group

userdel [-r] username  # -r deletes HOME directorygroupdel groupname

Network and Processes

ifconfig: View IP

ifconfig

ping: Test network connectivity

ping [-c count] IP or domain name# Example: ping -c 3 baidu.com

ps: View processes

ps -ef | grep process name

kill: Terminate process

kill [-9] process ID# -9: Force terminate

Environment Variables

Temporary Setting

export variable name=value

Permanent Setting

• User level: Edit ~/.bashrc

• Global level: Edit /etc/profile

View Environment Variables

echo $PATH

Compression and Decompression

tar: Compress/Decompress

# Compress: tar -zcvf archive name.tar.gz file1 file2# Decompress: tar -zxvf archive name.tar.gz [-C target directory]

zip/unzip

# Compress: zip [-r] archive name.zip file or directory# Decompress: unzip archive name.zip [-d target directory]

Other Commands

date: Display date

date "+%Y-%m-%d %H:%M:%S"  # Formatted output

wget/curl: Download files

wget file URLcurl -O file URL

top: Real-time monitor system status

top# Shortcuts: M (sort by memory), P (sort by CPU)

For more command help, you can use command –help or man command to view.

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