Ubuntu Server Guide Changes, errors and bugs This is the current edition for Ubuntu 20.04 LTS, Focal Fossa. Ubuntu serverguides for previous LTS versions: 18.04 (PDF), 16.04 (PDF). If you find any errors or have suggestions for improvements to pages, please use the link at thebottomof each topic titled: “Help improve this document in the forum.” This link will take you to the Server Discourse forum for the specific page you are viewing. There you can share your comments or let us know aboutbugs with each page. Offline Download this guide as a PDF Support There are a couple of different ways that Ubuntu Server Edition is supported: commercial support and community support. The main commercial support (and development funding) is available from Canonical, Ltd. They supply reasonably- priced support contracts on a per desktop or per server basis. For more information see the Ubuntu Advantage page. Community support is also provided by dedicated individuals and companies that wish to make Ubuntu the best distribution possible. Support is provided through multiple mailing lists, IRC channels, forums, blogs, wikis, etc. The large amount of information available can be overwhelming, but a good search engine query can usually provide an answer to your questions. See the Ubuntu Support page for more information. Basic installation This chapter provides an overview of installing Ubuntu 20.04 Server Edition. There is more detailed docu- mentation on other installer topics. Preparing to Install This section explains various aspects to consider before starting the installation. System requirements Ubuntu 20.04 Server Edition provides a common, minimalist base for a variety of server applications, such as file/print services, web hosting, email hosting, etc. This version supports four 64-bit architectures: • amd64 (Intel/AMD 64-bit) • arm64 (64-bit ARM) • ppc64el (POWER8 and POWER9) • s390x (IBM Z and LinuxONE) The recommended system requirements are: • CPU: 1 gigahertz or better 1 • RAM: 1 gigabyte or more • Disk: a minimum of 2.5 gigabytes Server and Desktop Differences The Ubuntu Server Edition and the Ubuntu Desktop Edition use the same apt repositories, making it just as easy to install a server application on the Desktop Edition as on the Server Edition. One major difference is that the graphical environment used for the Desktop Edition is not installed for the Server. This includes the graphics server itself, the graphical utilities and applications, and the various user-supporting services needed by desktop users. Backing Up Before installing Ubuntu Server Edition you should make sure all data on the system is backed up. If this is not the first time an operating system has been installed on your computer, it is likely you willneed to re-partition your disk to make room for Ubuntu. Any time you partition your disk, you should be prepared to lose everything on the disk should you make a mistake or something goes wrong during partitioning. The programs used in installation are quite reliable, most have seen years of use, but they also perform destructive actions. Preparing install media There are platform specific step-by-step examples for s390x LPAR, z/VM and ppc64el installations. For amd64, download the install image from https://releases.ubuntu.com/20.04/. There are many ways to boot the installer but the simplest and commonest way is to create a bootable USB stick to boot the system to be installed with (tutorials for other operating systems are also available). Booting the installer Plug the USB stick into the system to be installed and start it. Most computers will automatically boot from USB or DVD, though in some cases this is disabled to improve boot times. If you don’t see the boot message and the “Welcome” screen which should appear after it, you will need to set your computer to boot from the install media. There should be an on-screen message when the computer starts telling you what key to press for settings or a boot menu. Depending on the manufacturer, this could be Escape, F2,F10 or F12. Simply restart your computer and hold down this key until the boot menu appears, then select the drive with the Ubuntu install media. If you are still having problems, check out the Ubuntu Community documentation on booting from CD/DVD. After a few moments, the installer will start in its language selection screen. welcome_c|690x517 2 Using the installer The installer is designed to be easy to use and have sensible defaults so for a first install you can mostly just accept the defaults for the most straightforward install: • Choose your language • Update the installer (if offered) • Select your keyboard layout • Do not configure networking (the installer attempts to configure wired network interfaces viaDHCP, but you can continue without networking if this fails) • Do not configure a proxy or custom mirror unless you have to in your network • For storage, leave “use an entire disk” checked, and choose a disk to install to, then select “Done” on the configuration screen and confirm the install • Enter a username, hostname and password • Just select Done on the SSH and snap screens • You will now see log messages as the install is completed • Select restart when this is complete, and log in using the username and password provided There is more detailed documentation on all these options. Advanced Installation Software RAID Redundant Array of Independent Disks “RAID” is a method of using multiple disks to provide different balances of increasing data reliability and/or increasing input/output performance, depending on the RAID level being used. RAID is implemented in either software (where the operating system knows about both drives and actively maintains both of them) or hardware (where a special controller makes the OS think there’s only one drive and maintains the drives ‘invisibly’). The RAID software included with current versions of Linux (and Ubuntu) is based on the ‘mdadm’ driver and works very well, better even than many so-called ‘hardware’ RAID controllers. This section will guide you through installing Ubuntu Server Edition using two RAID1 partitions on two physical hard drives, one for / and another for swap. RAID Configuration Follow the installation steps until you get to the Guided storage configuration step, then: Select Custom storage layout. Create the /boot partition in a local disk. So select one of the devices listed in available devices and Add GPT Partition. Next, enter the partition size, then choose the desired Format (ext4) and /boot as mount point. And finally, select Create. Now to create the RAID device select Create software RAID (md) under AVAILABLE DEVICES. Add the name of the RAID disk (the default is md0). For this example, select “1 (mirrored)” in RAID level, but if you are using a different setup choose the appropriate type (RAID0 RAID1 RAID5 RAID6 RAID10). Note In order to use RAID5, RAID6 and RAID10 you need more than two drives. Using RAID0 or RAID1 only two drives are required. 3 Select the devices that will be used by this RAID device. The real devices can be marked as active or spare, by default it becomes active when is selected. Select the Size of the RAID device. Select Create. The new RAID device (md0 if you did not change the default) will show up in the available devices list, with software RAID 1 type and the chosen size. Repeat steps above for the other RAID devices. Partitioning Select the RAID 1 device created (md0) then select “Add GPT Partition”. Next, select the Size of the partition. This partition will be the swap partition, and a general rule for swap size is twice that of RAM. Enter the partition size, then choose swap in Format. And finally, select Create. Note A swap partition size of twice the available RAM capacity may not always be desirable, especially on systems with large amounts of RAM. Calculating the swap partition size for servers is highly dependent on how the system is going to be used. For the / partition once again select the RAID 1 device then “Add GPT Partition”. Use the rest of the free space on the device, choose the format (default is ext4) and select / as mount point, then Create. Repeat steps above for the other partitions. Once it is finished select “Done”. The installation process will then continue normally. Degraded RAID At some point in the life of the computer a disk failure event may occur. When this happens, using Software RAID, the operating system will place the array into what is known as a degraded state. If the array has become degraded, due to the chance of data corruption, by default Ubuntu Server Edition will boot to initramfs after thirty seconds. Once the initramfs has booted there is a fifteen second prompt giving you the option to go ahead and boot the system, or attempt manual recover. Booting to the initramfs prompt may or may not be the desired behavior, especially if the machine is in a remote location. Booting to a degraded array can be configured several ways: • The dpkg-reconfigure utility can be used to configure the default behavior, and during the processyou will be queried about additional settings related to the array. Such as monitoring, email alerts, etc. To reconfigure mdadm enter the following: sudo dpkg−reconfigure mdadm • The dpkg−reconfigure mdadm process will change the /etc/initramfs−tools/conf.d/mdadm configura- tion file. The file has the advantage of being able to pre-configure the system’s behavior, andcanalso be manually edited: BOOT_DEGRADED=true 4 Note The configuration file can be overridden by using a Kernel argument. • Using a Kernel argument will allow the system to boot to a degraded array as well: – When the server is booting press Shift to open the Grub menu.