Linux Command Line
The CLI is the primary way to interact with Linux servers. Mastering it is essential for system administration and automation.
Basic Commands
Navigation: pwd, cd, ls (-l, -a). File ops: cp, mv, rm (-r), mkdir, touch. Viewing: cat, less, head, tail (-f for live).
File Permissions
Owner/group/others with read/write/execute. chmod (755 or u+x), chown, chgrp. SUID, SGID, sticky bit for special permissions. Critical for security.
Text Processing
grep (search patterns), sed (stream editor), awk (structured text), sort, uniq, wc, cut, tr. Combine powerfully through pipes.
Pipes and Redirection
Pipes (|) chain commands: cat file | grep error | wc -l. Redirection: > (overwrite), >> (append), < (input), 2> (stderr). Unix philosophy: small tools combined.
Process Management
ps (list), top/htop (real-time), kill (signals), & (background), nohup (persist after logout), systemctl (services).
Shell Scripting
Bash scripts automate commands. #!/bin/bash shebang. Variables, conditionals (if/fi), loops (for/do/done), functions, command substitution ($(cmd)). Powerful automation.
Summary
The Linux CLI is essential for administration. File operations, permissions, text processing, pipes, process management, and scripting enable efficient system management.