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Linux Essential Commands

man: manual page.
- Explains how to use a shell command.
- For example, to find out how to use man, type man man
passwd: modify a user's password
ls: list directory content
cd: change directory
pwd: return working directory name
wc: word, line, character, and byte count
head: display first lines of a file
tail: display the last part of a file
cat: concatenate and print the file
more: display output one screen at a time
cp: cope file
mv: move file
rm: remove directory entries (like delete)
chmod: change file modes or Access Control Lists
- (u,g,o): user, group, other
- (r,w,x): read, write, execute
chown: change file owner or group
mkdir: make directories
rmdir: remove directories
ssh: OpenSSH SSH client (remote login program)
scp: secure copy (remote file copy program)
- -p: 保留原始檔案權限＆修改日期等
- -r: 複製整個資料夾
2>&1: send STDERR to STDOUT (0:STDIN, 1:STDOUT, 2:STDERR)
&: running job in background
nohup: 系統背景執行（不同於&）
- nohup <COMMAND> &
free -g: 查看實際剩餘ram
grep: find keywords in file
- grep <KEYWORD> <FILENAME>