What is a System Administrator

• A system administrator is responsible for the upkeep, configuration, and reliable operation of computer systems, especially multi-user computers like serves.

Essential Duties of System Administrator

• Main tasks include controlling access, adding hardware, automating tasks, overseeing backups, installing and upgrading software
• Also includes monitoring, troubleshooting, maintaining local documentation, vigilantly monitoring security, and tuning performance
• Additional tasks are developing site policies, working with vendors, and firefighting.
• A team can distribute these duties among members, but at least one person should understand all components and ensure every task is performed correctly.

Linux Distributions

• Consists of the Linux kernel, acting as the core of the operating system
• Also includes packages that provide all the commands executable on the system.
• All share the same kernel lineage
• Differences exist in format, type, and the number of packages
• They vary in their focus, support, and popularity.

Distributions of Linux

• Hundreds exist
• Distributions derived from Debian and Red Hat lineages are predominant in production
• The differences among distributions are not cosmically significant
• They each claim "easy installation" and "a massive software library" as distinguishing features

Key Considerations for Linux Distros

• Most include painless installation, a desktop environment, and some form of package management
• You can try them out easily via cloud instance or local virtual machine
• By adopting a distribution, you are making an investment in a particular vendor's way of doing things
• Organizations should consider how they will work with the vendor

Questions to ask before choosing a Linux Distro

• Is this distribution going to be around in five years?
• Is this distribution going to stay on top of the latest security patches?
• Does this distribution have an active community and sufficient documentation?
• If problems arise, will the vendor provide support, and at what cost?

Popular Linux Distros

• Arch ideal for those comfortable with the command line
• CentOS is a free analog of Red Hat Enterprise
• CoreOS specializes in containers
• Debian emphasizes freedom as a GNUish distro
• Fedora serves a a test bed for Red Hat Linux
• Kali is tailored for penetration testers
• Linux Mint is Ubuntu-based and desktop-friendly
• openSUSE is a free analog of SUSE Linux Enterprise; OpenWRT specializes in routers and embedded devices
• Oracle Linux is supported by Oracle and based on RHEL
• RancherOS is container-focused, 20MiB in size
• Red Hat Enterprise offers reliable, slow-changing commercial solutions
• Slackware is a grizzled, long-surviving distro
• SUSE Linux Enterprise is strong in Europe, multilingual
• Ubuntu is a cleaned-up version of Debian

Linux Distros used in the Book

• Debian GNU/Linux
• Ubuntu Linux
• Red Hat Enterprise Linux (and its doppleganger CentOS)
• FreeBSD

Red Hat Enterprise Linux (RHEL)

• RHEL has been a dominant force in the Linux world for more than two decades
• Their distributions are widely used in North America and beyond
• Red Hat, Inc., is the most successful open source software company in the world
• RHEL targets production at large enterprises that require support and consulting to keep their systems running smoothly
• RHEL is open source but requires a license
• Red Hat sponsors Fedora, a community-based distribution that tests software before integrating with RHEL

Notation conventions

• $ denotes a normal, unprivileged user's shell prompt

• denotes the root user's shell prompt

Shell-Style Globbing Characters

• A star (*) matches zero or more characters
• A question mark (?) matches one character
• A tilde (~) signifies the home directory of the current user
• ~user means the home directory of the specified user

Unit Decoding Examples

• A 1kB file contains 1,000 bytes
• 4KiB SSD pages contain 4,096 bytes
• 1GiB of RAM equals 1,073,741,824 bytes of memory
• A 6TB hard disk stores about 6,000,000,000,000 bytes

Manual Pages

• Man pages are read with the man command, and they are the traditional "on-line" documentation
• Program-specific man pages are included when new software packages are installed
• Man pages concisely describe individual commands, drivers, file formats, and library routines

Organization of Man Pages

• Linux divides man pages into sections
• Section 1: User-level commands and applications
• Section 2: System calls and kernel error codes
• Section 3: Library calls; Section 4: Device drivers and network protocols
• Section 5: Standard file formats; Section 6: Games and demonstrations
• Section 7: Miscellaneous files and documents
• Section 8: System administration commands
• Section 9: Obscure kernel specs and interfaces
• The exact structure isn't important because man finds the page wherever it is

Man command

• man title formats a specific manual page and sends it to your terminal through more
• It can also be sent through less, or whatever program is specified in PAGER
• title is typically a command, device, filename, or library routine name
• Sections of the manual are searched roughly numerically, with sections 1 and 8 usually searched first
• man -k keyword or apropos keyword lists man pages with the keyword in their online synopses

Storage of man pages

• nroff input for man pages is stored in /usr/share/man and compressed with gzip to save space
• The man command knows how to decompress them on the fly

Other Authoritative Documentation

• Man pages are just a small part of the official documentation
• System-specific guides and most of the rest are scattered on the web

System-Specific Guides on the web

• Debian documentation is at debian.org/doc
• Ubuntu documentation is at help.ubuntu.com
• RHEL documentation is at redhat.com/docs
• CentOS documentation is at wiki.centos.org
• FreeBSD documentation is at freebsd.org/docs.html

Package-Specific Documentation

• Packages are maintained by third parties like the Internet Systems Consortium and the Apache Software Foundation
• These groups write their own documentation which include white papers, design rationales, and book- or pamphlet-length topics

Sources for Keeping Up-to-Date

• The following websites are resources to keep up to date on the latest tech
  • darkreading.com
  • devopsreactions.tumblr.com
  • linux.com
  • linuxfoundation.org
  • lwn.net
  • lxer.com
  • securityfocus.com
  • @SwiftOnSecurity
  • @nixcraft
  • everythingsysadmin.com
  • sysadvent.blogspot.com
  • oreilly.com/topics
  • schneier.com
• Social media like Twitter and Reddit have strong, engaged communities

Task-Specific Forums and Reference Sites

• The following websites are guides, tutorials, and articles about how to accomplish specific tasks on UNIX and Linux
  • wiki.archlinux.org
  • askubuntu.com
  • digitalocean.com
  • kernel.org
  • serverfault.com
  • serversforhackers.com

Conferences

• Conferences are a great way to network with other professionals, keep tabs on technology trends, take training classes, gain certifications, and learn about the latest service and products

Tech Conferences

• LISA: Large Installation System Administration
• Monitorama: Monitoring tools and Techniques
• OSCON: Long-running O'Reilly OSS conference
• SCALE: Southern California Linux Expo
• DefCon: Oldest and largest hacker convention
• Velocity: O'Reilly conference on web operations
• BSDCan: Everything BSD from novices to gurus
• re:Invent: AWS cloud computing conference
• VMWorld: Virtualization and cloud computing
• LinuxCon: The future of Linux
• RSA: Enterprise cryptography and infosec
• DevOpsDays: Ranges of topics on bridging the gap between development and operations
• QCon: A conference for software developers

Installing Software

• Modern operating systems divide their contents into packages independently
• The default installation includes a range of starter packages that you can expand and contract according to your needs

Determining if Software is Already Installed

• Determine if software is installed by using this command redhat$ rpm -q python python-2.7.5-18.el7_1.1.x86_64

Ways to install software

• If you do need to install additional software, you first need to determine the canonical name of the relevant software package
• The following examples show the installation of the tcpdump command redhat# sudo yum install tcpdump
• Build software from source code
  • Clone software from code hub, example included;redhat# sudo yum install tcpdump
• Software can also be installed from web script

Hosting Systems and Software

• Operating systems and software can be hosted in private data centers, at co-location facilities, on a cloud platform, or on some combination of those options
• The best choice for new projects is a public cloud provider
• Public cloud providers offer advantages over data centers, including:
  • No capital expenses and low initial operating costs
  • No need to install, secure, and manage hardware
  • On-demand adjustment of storage, bandwidth, and compute capacity
  • Ready-made solutions for common ancillary needs
  • Cheaper and simpler implementation of highly available/redundant systems

Specialization and Adjacent Disciplines

• System administrators don't exist in a vacuum
• Required to build and maintain a complex network is a team of experts
• The roles with which system administrators overlap include:
  • DevOps; Site reliability engineer; Security operations engineers; Network administrators
  • Database administrators; Network operations center (NOC) engineers; Data center technicians; Architects
• Some administrators choose to specialize in one or more of these areas
• The goal as a system administrator, or as a professional working in any of these related areas, is to achieve the objectives of an organization