Commonly Used Linux Commands

Basic Linux Commands

cd Command

# Switch to directory /root/Docements using absolute path
cd /root/Docements
# Switch to path directory in current directory using relative path, "." represents current directory
cd ./path
# Return to parent directory
cd ..

ls Command

# Command to view files and directories
ls
# List all files, including hidden files (files starting with .)
ls -a
# List all files including file attributes and permission data
ls -l

grep Command

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# Used to search and filter data in files
grep [-aciv] [--color=auto] 'search string' filename

Common Parameter Explanations:

-a: Search binary files as text files
-c: Count the number of times ‘search string’ is found
-i: Ignore case differences, treating uppercase and lowercase as the same
-v: Reverse selection, displaying lines that do not contain ‘search string’

# For example:
# Extract lines containing MANPATH from file /etc/man.config and highlight found keywords
grep --color=auto 'MANPATH' /etc/man.config
# Output content from ls -l output that contains the letters file (case insensitive)
ls -l | grep -i file

cp Command

Copy file command, common parameters as follows

-a: Copy file characteristics together
-p: Copy file attributes together instead of using default method, similar to -a, commonly used for backup
-i: If target file already exists, ask before overwriting
-r: Recursive continuous copy, used for directory copy operations
-u: Only copy when target file differs from source file

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cp -a file1 file2 # Copy file file1 to file2 with all file characteristics
cp -r file1 file2 file3 dir # Recursively copy files file1, file2, file3 to directory dir

mv Command

Rename file usage

mv file1 file2 # Rename file file1 to file2

Move one file or multiple files to a folder at once (the last target file must be a directory)

mv file1 file2 file3 dir # Move files file1, file2, file3 to directory dir

rm Command (Use Carefully!!!!!!)

Delete files or directories, common parameters

-f: Force, ignore non-existent files, no warning messages
-i: Interactive mode, ask user before deletion
-r: Recursive deletion, most commonly used for directory deletion, a very dangerous parameter

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rm -i file # Delete file, will ask before deletion
rm -fr dir # Force delete all files in directory dir

ps Command

View process execution status, commonly used combinations with other commands

ps aux # View all process data in system
ps ax # View all processes not related to terminal
ps -lA # View all process data in system
ps axjf # View with some process tree status
ps aux| grep -ic python # View all processes related to python in system

kill Command

Send signals to processes, commonly used signals as follows (can use code numbers instead of corresponding signals)

1: SIGHUP, start terminated process
2: SIGINT, equivalent to ctrl+c, interrupt program execution
9: SIGKILL, force interrupt process execution
15: SIGTERM, terminate process in normal way
17: SIGSTOP, equivalent to ctrl+z, pause process execution

kill -signal PID

# Terminate first background job in normal way, can use jobs command to view first job in background
kill -SIGTERM %1
# Restart process with ID PID, PID can be obtained using ps command with pipe and grep
kill -SIGHUP PID

tar Command

Package files. By default does not compress, but if corresponding parameters are specified, it will call corresponding compression programs (such as gzip and bzip) for compression and decompression. Common parameters:

-c: Create new package file
-t: View contents of package file
-x: Unpack or decompress function, can combine with -C (uppercase) to specify decompression directory. Note -c, -t, -x cannot appear in same command
-j: Compress/decompress through bzip2 support
-z: Compress/decompress through gzip support
-v: Display files being processed during compression/decompression
-f filename: filename is the file to be processed
-C dir: Specify compression/decompression directory dir

# Usually we only need to use the following three commands:
Compress: tar -jcv -f filename file or directory name to be processed
Query: tar -jtv -f filename
Decompress: tar -jxv -f filename -C directory to decompress to

cat Command

View text file content

cat test|less # View content in text file

chgrp/chown Command

Change user group/change file owner

chgrp/chown users -R ./dir # Recursively modify user group of all files in dir directory and subdirectories to users

chmod Command

Change file permissions Common permission representations:

-rw——- (600) Only owner has read and write permissions.
-rw-r–r– (644) Only owner has read and write permissions; group users and other users only have read permissions.
-rwx—— (700) Only owner has read, write, and execute permissions.
-rwxr-xr-x (755) Owner has read, write, and execute permissions; group users and other users only have read and execute permissions.
-rwx–x–x (711) Owner has read, write, and execute permissions; group users and other users only have execute permissions.
-rw-rw-rw- (666) All users have read and write permissions.
-rwxrwxrwx (777) All users have read, write, and execute permissions.

chmod -R 777 file # Set file to maximum permissions

View System Configuration

Open /proc directory to view system hardware configuration

// View cpu information
cat /proc/cpuinfo
// View memory
free -m
// View hard disk space
df -h

Advanced Linux Commands

curl Command

HTTP command line tool, supports file upload and download.

Basic Syntax:

curl [option] [url]

Common Usage Methods:

Testing

curl http://www.linux.com // Test connectivity between server and website

Download

curl -o filename http_url // Download file from url and save as filename

curl -O -u user_name:password ftp_url // Download file from ftp_url using user_name and password

Upload file

curl -T upload_file -u user_name:password ftp_url // Upload file to url using user_name and password

View public IP

curl ifconfig.me or curl cip.cc

View Current GPU Usage

nvdia-smi

Run Program Using Specified GPU

CUDA_VISIBLE_DEVICES={{number of interface}} python {{file}}.py

File Transfer Between Servers (scp command)

Server actually means computer, the two can be used interchangeably; {{}} represents parameters you need to modify

Copy files from remote server to local server

scp -r {{remote server name}}@{{remote server ip}}:{{remote server directory}} {{local server directory}}

Upload Files from Local Server to Remote Server

scp -r {{local server directory}} {{remote server name}}@{{remote server ip}}:{{remote server directory}}

Note: Common scp Command Parameters

-r Recursively copy entire directory.
-P port Note capital P, port specifies the port number for data transmission

Common scp Command Issues

Solution to WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED

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vim ~/.ssh/known_hosts
Delete the rsa information related to the unrecognizable server.

ssh Command

Remotely log in to Linux host

Most commonly used commands

ssh -p port user_name@hostname // Log in to host at specified port with specified user

servive sshd restart // Restart sshd service

vim /etc/ssh/sshd_config // Modify port number and other configurations in config file

apt-get

Install Software Without sudo Permissions

apt-get source your_package
cd your_package
./configure --prefix=$HOME
make
make install

Under root Account:

useradd user_name Create user user_name
passwd user_name Set password for user user_name
userdel user_name Delete user user_name
su user_name Switch to (switch user) user user_name

References and citations