Principles of System Administration. Jan Schaumann

Transcription

1 Principles of System Administration Jan Schaumann February 6, 2018

2 Contents Preface to the preface Preface i ii I Introduction and General Concepts 1 1 Introduction What exactly does a System Administrator do? The Profession of System Administration System Administration Education Challenges in System Administration Education The Three Pillars of Exceptional System Design Scalability Security Simplicity The Future of System Administration Problems and Exercises 23 Problems Exercises Unix Unix History The Operating System Networking Open Source Basic Unix Concepts and Features

3 CONTENTS The shell Manual pages and documentation A portable, multitasking, multiuser system The Unix Philosophy Problems and Exercises 50 Exercises Documentation Techniques System Documentation Writing Know Your Audience Online Documentation Di erent Document Types Processes and Procedures Policies Online Help and Reference Infrastructure Architecture and Design Program Specification and Software Documentation Collaboration Formats Problems and Exercises 68 II Fundamental Technologies and Concepts 70 4 Of File Systems and Storage Models Introduction Storage Models Direct Attached Storage Network Attached Storage Storage Area Networks Cloud Storage Storage Model Considerations Disk Devices and Interfaces Physical Disk Structure Dividing and Combining Disks Partitions

4 CONTENTS Logical Volumes RAID File Systems File System Types File System Layout The Unix File System Conclusions Problems and Exercises 122 Problems Software Installation and Package Management Introduction Types of Software Up and down the software stack Operating System vs. System Software vs. Third Party Software File System Layout OS Installation Identifying server requirements OS Installation Overview OS Installation Details Package Management Systems Manual Software Installation Software Installation by Package Manager Inherent Security Risks Managing Software Updates and Patches Conclusions Problems and Exercises 166 Problems Of Users and Groups Introduction Types of Users Groups of Users User Authentication Authentication Examples

5 CONTENTS The Problem with Passwords Sharing root Summary Problems and Exercises 188 Problems Configuration Management Introduction Services, not Single Points of Failure Defining Services and Requirements Example Service: Syslog Example Requirements: LDAP Client Configuration CM Requirements Of States and Sets States Sets Fighting entropy Deployment roles Idempotence and Convergence Quis custodiet ipsos custodes? Even more formal process definitions Summary Problems and Exercises 222 Problems Automation Introduction Of Laziness And Other Virtues Benefits of Automation Repeatability Reliability Flexibility Who benefits from automation? Ourselves Our Peers All Users

6 CONTENTS Levels of Automation Automation Pitfalls Increased Complexity and Impact Loss of Audit Trail Loss of Accountability Safeguards Summary Problems and Exercises 246 Problems Building Scalable Tools Introduction How Software evolves Scripts Programs Software Products Principles of Developing Robust System Tools Unix Philosophy and User Interface Principle of Least Astonishment Explicit and predictable failure There s no such thing as a temporary solution Readability counts Of Buses and Windows Code Reviews Additional Guidelines Summary Problems and Exercises 274 Problems Networking Security Authentication and Authorization

7 CONTENTS 6 III Managing Complex Services Managing System Services Backup, Failover, and Disaster Recovery File System Backups and Snapshots Monitoring and Visibility 284 IV Meta Matter Everything We Haven t Covered Containers Service Orchestration Ethics and Legal Issues Future Direction of System Administration 289 Glossary of Terms 290 A Image Attributions 291 Index 294

8 Listings 1 Sample command-line invocations vi 2.1 Simple I/O redirection in the shell Simple job control in the shell clause BSD license fdisk(8) sample invocation and output on a Linux system disklabel(8) invocation and output on a NetBSD system Absolute and relative pathnames Output of ls -ai Output of stat(1) Excerpt of the boot messages of a NetBSD Xen domu booting in Amazon EC Excerpt of the boot messages of a NetBSD system Excerpt of the hier(7) manual page Commands used during the installation of NetBSD rpm/yum sample commands pkgrsc sample commands Excerpt of a typical /etc/passwd file on a NetBSD system Password authentication on the console SSH key authentication Kerberos authentication SSHCA and MFA example Excerpt of a Puppet manifest defining the syslog service Excerpt of an LDAP client authentication Chef recipe A CFEngine agent bundle Idempotent and non-idempotent commands Script to build GCC on an old IRIX system The Zen of Python rc(8) key=value pair configuration

9 LISTINGS Code Sample: Simple is better than complex

10 List of Figures 1.1 Anthora Co ee Cup An IBM 704 mainframe Unix genealogy tree Standard streams in a simple pipeline Di erent systems running Unix Direct Attached Storage Three hosts using Network Attached Storage, or NAS NAS and SAN Hardware SAN illustrated Cloud Storage HDD vs. SSD Physical Disk Structure Logical Volume Management RAID Levels illustrated Apple Xserve RAID File System Hierarchy UFS Details File Metadata A typical POST and BIOS screen Second stage boot loader examples Types of Software OpenSolaris Installation Software Dependency Tree Screengrabs of tweets illustrating the circular dependencies of language-specific package managers ca