PebbleRack

Guide 05 of 25 · beginner

Install Ubuntu Server LTS on a lab host

Install Ubuntu Server 26.04.1 LTS on a clearly identified, backed-up machine and record a first-boot baseline.

Source-verified · Not lab-testedOfficial sources checked 2026-09-29. No PebbleRack hardware compatibility claim.

Outcome

A dedicated lab host boots Ubuntu Server 26.04.1 LTS, receives a network address, and accepts a local login. These steps assume an x86-64 machine with a disk you may erase and physical access to its screen and keyboard. Other architectures need their matching official image and device instructions.

Before you start

Complete guides 01–04. Move all important data off the target disk and test that the backup can be read elsewhere. Confirm the disk model and capacity in your private inventory. Have a USB drive you may erase for installation media. Connect the host by Ethernet if possible. Installation and USB image writing are destructive when the wrong target is chosen.

Steps

  1. Get the official image. From Canonical's Ubuntu Server download, choose the 26.04.1 LTS server image for your architecture. Also get the release's SHA256SUMS and signature file. Follow Canonical's verification procedure to authenticate the checksum file and compare the ISO hash. Stop if verification fails.
  2. Write the USB installer. Use a trusted image-writing tool, selecting the USB device by its size and label. Confirm that it is the USB device, not a data disk. Writing an ISO is not the same as copying it as a normal file. Eject it when complete.
  3. Boot from USB. Attach screen and keyboard. Use the host vendor's boot menu to select the USB drive. If the installer cannot see the target disk or network adapter, stop and check the exact hardware and firmware settings. Do not repeatedly switch storage controller modes on a machine with an existing OS.
  4. Use simple first-install settings. Choose language and keyboard. Let a wired network use DHCP. Leave proxy and custom mirror blank unless your network requires them. For storage, select only the disk identified in the inventory. Review the installer's final storage summary before confirming erase and format. Do not install onto a shared or uncertain disk.
  5. Create an administrator account. Use a unique username and a strong password stored in your password manager. Give the host the name chosen in guide 04. You may select the installer option for OpenSSH if offered; guide 06 covers verifying and securing access. Skip optional application snaps for this first baseline.
  6. Reboot and record evidence. Remove the USB stick when prompted. Log in locally and run cat /etc/os-release, hostnamectl, ip address, ip route, and df -h. Record the release, hostname, network interface, mounted filesystems, and date in private notes. Keep credentials out of that log.
  7. Check for updates. Run sudo apt update followed by sudo apt upgrade. Read the proposed changes before accepting. If the host signals a reboot is required, schedule and perform it while local access is available.

Check it worked

The host boots from its internal disk without the installer USB, local login succeeds, /etc/os-release identifies Ubuntu 26.04, and the host has the expected route and DNS behavior. Your private record names the disk that was used. This has not verified any AI workload or PebbleRack hardware.

If it fails / rollback

If the installer fails before disk changes, return to the original boot device and recheck image, USB media, firmware, and disk health. If formatting already occurred, restoring the prior system requires your pre-install backup; the installer has no universal undo. If networking fails, use the local console and guide 04's router baseline.

Safety and data notes

Never paste a password, recovery key, complete disk inventory, or router screenshot into public support. Do not run installer commands copied from an unverified source. A minimum installation requirement is not an application sizing guarantee.

Sources

  • Ubuntu, Server download — current 26.04.1 LTS image and requirements; checked 2026-09-29.
  • Ubuntu Server, basic installation — installer flow and disk warning; checked 2026-09-29.
  • Ubuntu, verify your download — signed checksums and ISO verification; checked 2026-09-29.

Next guide

Continue to guide 06, “Use SSH keys for lab administration.”