SUSE Linux Enterprise Desktop 15 SP2 Administration Guide Administration Guide SUSE Linux Enterprise Desktop 15 SP2 Covers system administration tasks like maintaining, monitoring and customizing an initially installed system. Publication Date: September 24, 2021 SUSE LLC 1800 South Novell Place Provo, UT 84606 USA https://documentation.suse.com Copyright © 2006– 2021 SUSE LLC and contributors. All rights reserved. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or (at your option) version 1.3; with the Invariant Section being this copyright notice and license. A copy of the license version 1.2 is included in the section entitled “GNU Free Documentation License”. For SUSE trademarks, see https://www.suse.com/company/legal/ . All other third-party trademarks are the property of their respective owners. Trademark symbols (®, ™ etc.) denote trademarks of SUSE and its aliates. Asterisks (*) denote third-party trademarks. All information found in this book has been compiled with utmost attention to detail. However, this does not guarantee complete accuracy. Neither SUSE LLC, its aliates, the authors nor the translators shall be held liable for possible errors or the consequences thereof. Contents About This Guide xviii 1 Available Documentation xix 2 Giving Feedback xx 3 Documentation Conventions xxi 4 Product Life Cycle and Support xxii Support Statement for SUSE Linux Enterprise Desktop xxiii • Technology Previews xxiv I COMMON TASKS 1 1 Bash and Bash Scripts 2 1.1 What is “The Shell”? 2 Bash Configuration Files 2 • The Directory Structure 5 1.2 Writing Shell Scripts 9 1.3 Redirecting Command Events 10 1.4 Using Aliases 11 1.5 Using Variables in Bash 12 Using Argument Variables 13 • Using Variable Substitution 13 1.6 Grouping and Combining Commands 14 1.7 Working with Common Flow Constructs 15 The if Control Command 15 • Creating Loops with the for Command 16 1.8 For More Information 16 2 sudo Basics 17 2.1 Basic sudo Usage 17 Running a Single Command 17 • Starting a Shell 18 iii Administration Guide 2.2 Configuring sudo 19 Editing the Configuration Files 19 • Basic sudoers Configuration Syntax 20 • Basic sudoers Rules 21 2.3 sudo Use Cases 23 Using sudo without root Password 23 • Using sudo with X.Org Applications 24 2.4 Further Information 25 3 YaST 26 3.1 YaST Topics 26 3.2 YaST Interface Overview 27 3.3 Useful Key Combinations 27 4 YaST in Text Mode 29 4.1 Navigation in Modules 30 4.2 Advanced Key Combinations 31 4.3 Restriction of Key Combinations 32 4.4 YaST Command Line Options 32 Installing Packages from the Command Line 33 • Working with Individual Modules 33 • Command Line Parameters of YaST Modules 33 5 YaST Online Update 58 5.1 The Online Update Dialog 59 5.2 Installing Patches 60 5.3 Automatic Online Update 61 6 Managing Software with Command Line Tools 64 6.1 Using Zypper 64 General Usage 64 • Using Zypper Subcommands 66 • Installing and Removing Software with Zypper 66 • Updating Software with Zypper 71 • Identifying Processes and iv Administration Guide Services Using Deleted Files 75 • Managing Repositories with Zypper 76 • Querying Repositories and Packages with Zypper 78 • Showing Life Cycle Information 80 • Configuring Zypper 81 • Troubleshooting 82 • Zypper Rollback Feature on Btrfs File System 82 • For More Information 82 6.2 RPM—the Package Manager 82 Verifying Package Authenticity 83 • Managing Packages: Install, Update, and Uninstall 84 • Delta RPM Packages 85 • RPM Queries 86 • Installing and Compiling Source Packages 88 • Compiling RPM Packages with build 90 • Tools for RPM Archives and the RPM Database 91 7 System Recovery and Snapshot Management with Snapper 92 7.1 Default Setup 93 Default Settings 94 • Types of Snapshots 94 • Directories That Are Excluded from Snapshots 95 • Customizing the Setup 96 7.2 Using Snapper to Undo Changes 99 Undoing YaST and Zypper Changes 100 • Using Snapper to Restore Files 105 7.3 System Rollback by Booting from Snapshots 107 Snapshots after Rollback 109 • Accessing and Identifying Snapshot Boot Entries 109 • Limitations 111 7.4 Enabling Snapper in User Home Directories 112 Installing pam_snapper and Creating Users 113 • Removing Users 113 • Manually Enabling Snapshots in Home Directories 114 7.5 Creating and Modifying Snapper Configurations 114 Managing Existing Configurations 116 7.6 Manually Creating and Managing Snapshots 119 Snapshot Metadata 119 • Creating Snapshots 121 • Modifying Snapshot Metadata 122 • Deleting Snapshots 122 v Administration Guide 7.7 Automatic Snapshot Clean-Up 124 Cleaning Up Numbered Snapshots 124 • Cleaning Up Timeline Snapshots 126 • Cleaning Up Snapshot Pairs That Do Not Differ 127 • Cleaning Up Manually Created Snapshots 128 • Adding Disk Quota Support 128 7.8 Showing Exclusive Disk Space Used by Snapshots 129 7.9 Frequently Asked Questions 131 8 Live kernel patching with KLP 133 8.1 Advantages of Kernel Live Patching 133 8.2 Kernel Live Patching overview 133 Kernel Live Patching scope 135 • Kernel Live Patching limitations 135 8.3 Activating Kernel Live Patching using YaST 135 8.4 Activating Kernel Live Patching from the command line 136 8.5 Performing Kernel Live Patching 137 Checking expiration date of the live patch 137 8.6 Troubleshooting Kernel Live Patching issues 138 Manual patch downgrade 138 9 Transactional Updates 139 9.1 Limitations of Technology Preview 139 9.2 Enabling transactional-update 141 9.3 Managing Automatic Updates 141 9.4 The transactional-update Command 142 9.5 Troubleshooting 144 10 Remote Graphical Sessions with VNC 145 10.1 The vncviewer Client 145 Connecting Using the vncviewer CLI 145 • Connecting Using the vncviewer GUI 146 • Notification of Unencrypted Connections 146 vi Administration Guide 10.2 Remmina: the Remote Desktop Client 146 Installation 146 • Main Window 147 • Adding Remote Sessions 147 • Starting Remote Sessions 149 • Editing, Copying, and Deleting Saved Sessions 150 • Running Remote Sessions from the Command Line 150 10.3 Configuring One-time Sessions on the VNC Server 151 Available Configurations 152 • Initiating a One-time VNC Session 153 • Configuring One-time VNC Sessions 153 10.4 Configuring Persistent VNC Server Sessions 154 VNC Session Initiated Using vncserver 155 • VNC Session Initiated Using vncmanager 156 10.5 Configuring Encryption on the VNC Server 159 11 File Copying with RSync 162 11.1 Conceptual Overview 162 11.2 Basic Syntax 162 11.3 Copying Files and Directories Locally 163 11.4 Copying Files and Directories Remotely 164 11.5 Configuring and Using an Rsync Server 164 11.6 For More Information 167 II BOOTING A LINUX SYSTEM 168 12 Introduction to the Boot Process 169 12.1 Terminology 169 12.2 The Linux Boot Process 170 The Initialization and Boot Loader Phase 170 • The Kernel Phase 171 • The init on initramfs Phase 174 • The systemd Phase 176 vii Administration Guide 13 UEFI (Unified Extensible Firmware Interface) 177 13.1 Secure Boot 177 Implementation on SUSE Linux Enterprise Desktop 178 • MOK (Machine Owner Key) 180 • Booting a Custom Kernel 181 • Using Non-Inbox Drivers 183 • Features and Limitations 184 13.2 For More Information 185 14 The Boot Loader GRUB 2 186 14.1 Main Differences between GRUB Legacy and GRUB 2 186 14.2 Configuration File Structure 186 The File /boot/grub2/grub.cfg 187 • The File /etc/default/ grub 188 • Scripts in /etc/grub.d 191 • Mapping between BIOS Drives and Linux Devices 192 • Editing Menu Entries during the Boot Procedure 193 • Setting a Boot Password 194 14.3 Configuring the Boot Loader with YaST 195 Boot Loader Location and Boot Code Options 196 • Adjusting the Disk Order 198 • Configuring Advanced Options 199 14.4 Helpful GRUB 2 Commands 201 14.5 More Information 203 15 The systemd Daemon 204 15.1 The systemd concept 204 Unit File 205 15.2 Basic Usage 206 Managing Services in a Running System 206 • Permanently Enabling/ Disabling Services 208 15.3 System Start and Target Management 210 Targets Compared to Runlevels 210 • Debugging System Start- Up 213 • System V Compatibility 216 15.4 Managing Services with YaST 217 viii Administration Guide 15.5 Customizing systemd 218 Customizing Unit Files 218 • Creating drop-in files 219 • Converting xinetd services to systemd 220 • Creating Custom Targets 221 15.6 Advanced Usage 222 Cleaning Temporary Directories 222 • System Log 223 • Snapshots 223 • Loading Kernel Modules 223 • Performing Actions before Loading a Service 224 • Kernel Control Groups (cgroups) 225 • Terminating Services (Sending Signals) 226 • Important Notes on the D-Bus Service 226 • Debugging Services 227 15.7 systemd timer units 228 systemd timer types 229 • systemd timers and service units 229 • Practical example 229 • Managing systemd timers 231 15.8 More Information 231 III SYSTEM 232 16 32-Bit and 64-Bit Applications in a 64-Bit System Environment 233 16.1 Runtime Support 233 16.2 Kernel Specifications 234 17 journalctl: Query the systemd Journal 235 17.1 Making the Journal Persistent 235 17.2 journalctl Useful Switches 236 17.3 Filtering the Journal Output 237 Filtering Based on a Boot Number 237 • Filtering Based on Time Interval 237 • Filtering Based on Fields 238 17.4 Investigating systemd Errors 239 17.5 Journald Configuration 240 Changing the Journal Size Limit 240 • Forwarding the Journal to /dev/ ttyX 240 • Forwarding the Journal to Syslog Facility 241 ix Administration Guide 17.6 Using YaST to Filter the systemd Journal 241 17.7 Viewing Logs in GNOME 242 18 update-alternatives: Managing Multiple Versions of Commands and Files