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. 


.. toctree::
   :maxdepth: 2
   :glob: 

   Navigating the Linux Shell <1-nav>
   Interacting with Files on Pegasus <2-files>
   File Permissions in Linux <3-rwx>
   Access Control Lists – ACL <4-acl>

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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``