Linux Guides

Introduction to Linux on Pegasus

Pegasus is currently running the CentOS 7.6 operating system, a distribution of Linux. Linux is a UNIX-like kernel, though in this document it will generally refer to the entire CentOS distribution. The three basic components of UNIX-like operating systems are the kernel, shell, and system programs. The kernel handles resource management and program execution. The shell interprets user commands typed at a prompt. System programs implement most operating system functionalities such as user environments and schedulers.

Everything in Linux is either a file (a collection of data) or a process (an executing program). Directories in Linux are types of files.

In the below examples, username represents your access account.

• Navigating the Linux Shell
  • View your current shell with echo:
  • View all environment variables with env:
  • View your current directory with pwd:
  • View the contents of a directory with ls:
  • Navigate to directories with cd:
  • View directory contents with tree:
  • Check command availability and location with which:
• Interacting with Files on Pegasus
  • Make directories with mkdir:
  • Remove directories with rmdir:
  • Remove files and directories with rm:
  • View file contents with cat:
  • Create files with cat and redirection:
  • View file contents with head and tail:
  • Rename and Move with mv:
  • Copy with cp:
  • Edit files : nano, emacs, vi:
  • View file contents by page with more and less:
• File Permissions in Linux
  • Understanding File Permission Categories
  • Changing File Permissions in Linux
  • Changing Group Ownership in Linux
• Access Control Lists – ACL
  • Getting ACL information
  • Setting ACL information
  • Removing ACL information

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Linux FAQs

How can I check my shell?

$ echo $SHELL or $ echo $0

How can I view my environment variables?

$ env or $ env | sort

How can I check command/software availability and location?

$ which executable, for example $ which vim

How can I get help with commands/software?

Use the Linux manual pages: $ man executable, for example $ man vim