Documentation Overview

  1. Operation documentation
    1. Installation
      1. Run UBOS on a PC (64bit)
      2. Run UBOS from a boot stick on a PC (64bit)
      3. Run UBOS in a VirtualBox virtual machine (64bit)
      4. Run UBOS on an Amazon Web Services EC2 virtual server
      5. Run UBOS on Raspberry Pi 5
      6. Run UBOS on ESPRESSObin
      7. Run UBOS in a Linux container on a PC (64bit)
      8. Run UBOS in an aarch64 Linux container
    2. Setting up your first Site and App
    3. Setting up networking and DNS
    4. How to create a website secured by SSL/TLS
    5. How to set up a website as a Tor hidden service
    6. Managing Sites and Apps
    7. Backup and restore
    8. Upgrading and keeping UBOS current
    9. The UBOS Staff
    10. App-specific notes
      1. Reliably send e-mail via Amazon Web Services’ Simple E-mail Service: amazonses
      2. Static website hosting with rsync-based upload: docroot
      3. Notes on Mastodon
      4. Notes on Nextcloud
      5. Notes on Redirect
      6. Notes on Wordpress
    11. Device-specific Notes
      1. ESPRESSObin
      2. Raspberry Pi
    12. Advanced management
      1. Enabling non-standard package repositories
      2. Migrating from one App to another
      3. Pinning resources
    13. Command reference
    14. FAQ, HOWTOs and Troubleshooting
      1. “Package not found error” when installing a new App or Accessory
      2. A UBOS container comes up degraded
      3. Booting UBOS on a PC starts out fine, but then the screen goes blank
      4. Can I run UBOS in a Docker container?
      5. Can I use UBOS without purchasing a domain name?
      6. Cannot access MySQL database. File missing: /etc/mysql/root-defaults-ubos.cnf
      7. Cannot boot UBOS from boot stick on a PC
      8. Cannot connect to the public internet from a UBOS container
      9. Cannot create a temporary backup; the backup directory is not empty
      10. Failed to create file /sys/devices/system/cpu/microcode/reload
      11. How are the various UBOS images different from each other?
      12. How can I install more than one web App on the same Device?
      13. How do I set up WiFi?
      14. How to enable non-standard Package Repositories
      15. How to get help
      16. How to log into your UBOS Device
      17. How to modify the configuration of your Site
      18. How to report a bug or issue
      19. How to use Pagekite to reach your UBOS Device behind a firewall
      20. How to use SSH
      21. I need a Package that isn’t in UBOS
      22. I need root
      23. I own a domain name, and I’d like to use it for my UBOS Device. How do I do that?
      24. I want to move from one device to another, or from/to the cloud to/from a device
      25. I want to run ssh on a non-standard port
      26. I’m running out of disk space, what now?
      27. Installing a new Package or updating fails with a message about “invalid or corrupted package” or “key is disabled”
      28. Installing a new Package or upgrading fails with a message about “unknown trust”
      29. Is it safe to have my Site accessible from the public web?
      30. My non-English keyboard layout is all screwed up
      31. My SD card is much larger than the UBOS image. How do I use the rest of the space?
      32. Nothing happens when UBOS is supposed to be booting
      33. Problems with “IPv6 Packet Filtering Framework”
      34. UBOS is in a “degraded” state
      35. ubos-admin status reports “Systemd unit … has failed”
      36. Verify your downloaded UBOS image
      37. What is the default “root” password?
      38. What text editor can I use on UBOS?
      39. Why did you derive UBOS Linux from Arch Linux, and what is the relationship between UBOS Linux and Arch?
      40. Why is it called UBOS?
      41. Writing a disk image to a USB stick or SD card
        1. Writing an image to a USB stick or SD card on Linux
        2. Writing an image to a USB stick or SD card on macOS
        3. Writing an image to a USB stick or SD card on Windows
  2. Developer documentation
    1. Developer setup
      1. Developing using Arch Linux on VirtualBox x86_64 with a systemd-nspawn container
      2. Developing using a UTM Arch Linux VM on Apple Silicon computers with UBOS in a systemd-nspawn container
      3. Alternate developer setups
        1. Developing using a systemd-nspawn container (Linux host only)
        2. Developing using Arch Linux using Parallels on Apple Silicon with a systemd-nspawn container
        3. Developing using a UTM Arch Linux VM on Apple x86_64 computers with UBOS in a systemd-nspawn container
    2. Developer tutorials for standalone UBOS apps (not UBOS Mesh)
      1. Build and run your first UBOS standalone App
      2. How to package UBOS standalone Apps built with a variety of languages
        1. Hello World
        2. Glad-I-Was-Here (PHP, Mariadb)
        3. An Accessory for Glad-I-Was-Here (PHP, MySQL)
        4. Glad-I-Was-Here (PHP, Postgresql)
        5. Glad-I-Was-Here (Java, Mariadb)
        6. Glad-I-Was-Here (Python, MySQL)
    3. UBOS Gears Reference
      1. UBOS Manifest
        1. Structure of the UBOS Manifest
        2. Info section
        3. Roles section
        4. Customization points section
        5. Appinfo section
        6. Accessoryinfo section
        7. Variables available at deploy or undeploy
        8. Functions that may be applied to variables
        9. Creating random values
        10. Scripts in UBOS Manifests
      2. Site JSON
      3. A complex deployment example
      4. UBOS Networking
      5. Allocating and opening up non-default ports
      6. Logging
      7. UBOS state
      8. UBOS Backup format
      9. Format of the App Status JSON
      10. Testing standalone Apps with “webapptest”
      11. Understanding ubos-admin
        1. Command: ubos-admin backup
        2. Command: ubos-admin backupinfo
        3. Command: ubos-admin createsite
        4. Command: ubos-admin deploy
        5. Command: ubos-admin hostid
        6. Command: ubos-admin init-staff
        7. Command: ubos-admin list-data-transfer-protocols
        8. Command: ubos-admin listnetconfigs
        9. Command: ubos-admin listsites
        10. Command: ubos-admin read-configuration-from-staff
        11. Command: ubos-admin restore
        12. Command: ubos-admin setnetconfig
        13. Command: ubos-admin setup-shepherd
        14. Command: ubos-admin showappconfig
        15. Command: ubos-admin shownetconfig
        16. Command: ubos-admin showsite
        17. Command: ubos-admin status
        18. Command: ubos-admin undeploy
        19. Command: ubos-admin update
        20. Command: ubos-admin write-configuration-to-staff
    4. Release channels and UBOS release process
    5. Miscellaneous
      1. Potentially useful infrastructure for standalone Apps
        1. The UBOS rsync server
      2. Middleware-specific notes
        1. Node.js notes
        2. SMTP notes
      3. Setting up an Arch Linux system as a UBOS development system
        1. How to create a UBOS development VM for VirtualBox on x86_64
        2. How to create a UBOS development VM for UTM on x86_64 Apple computers
        3. How to create a UBOS development VM for UTM on Apple Silicon computers
        4. How to create a UBOS development VM for Parallels Desktop on Apple Silicon computers
      4. Creating cloud images
        1. Amazon Web Services EC2
    6. Developer FAQ
      1. Doesn’t apt / dpkg / yum / pacman etc. does what UBOS Gears does already?
      2. Doesn’t puppet / chef / ansible etc. does what UBOS Gears does already?
      3. Doesn’t Docker do what UBOS Gears does already?
      4. Is it possible to run UBOS Gears or Mesh on an operating system other than UBOS Linux?
      5. Can I manage apps packaged as Docker containers with UBOS?
  3. Architecture
  4. Glossary
    1. Accessory
    2. App
    3. AppConfigId
    4. AppConfigItem
    5. AppConfiguration
    6. Arch
    7. Arch Linux
    8. Attribute
    9. blessing
    10. Bot
    11. Context Path
    12. Customization Point
    13. Data Transfer Protocol
    14. Deployment
    15. Depot
    16. Device
    17. Device Class
    18. diet4j module framework
    19. EntityType
    20. Flock
    21. Gradle
    22. Handlebars
    23. History
    24. Home Server
    25. HostId
    26. Hostname
    27. IDE
    28. Installation
    29. LetsEncrypt
    30. mDNS
    31. MeshBase
    32. MeshObject
    33. MeshObjectIdentifier
    34. MeshType
    35. MeshTypeIdentifier
    36. Middleware
    37. Model
    38. Network Configuration
    39. Package
    40. Pagekite
    41. Parallels Desktop
    42. Personal Server
    43. PKGBUILD
    44. Property
    45. PropertyType
    46. Relationship
    47. RelationshipType
    48. Release Channel
    49. Repository
    50. Retention Bucket
    51. Role
    52. RoleAttribute
    53. RoleProperty
    54. RoleType
    55. Rolling Release
    56. Shepherd
    57. Site
    58. Site JSON
    59. Site JSON Template
    60. SiteId
    61. Transaction
    62. Transaction Log
    63. UBOS Gears
    64. UBOS Linux
    65. UBOS Manifest
    66. UBOS Mesh
    67. UBOS Mesh code generator
    68. UBOS Project
    69. UBOS Staff
    70. unblessing
    71. UTM
    72. VirtualBox
    73. VMWare
    74. Wildcard hostname

Glad-I-Was-Here (Java, Mariadb)



The Java version of Glad-I-Was-Here is functionally equivalent to Glad-I-Was-Here (PHP, Mariadb). However, it is implemented using Java servlets and runs under Tomcat. It also uses diet4j for Java module management.

If you have not already read through Glad-I-Was-Here (PHP, Mariadb), we recommend you do so first as we’ll only discuss things in this section that were not covered before.

To obtain the source code:

% git clone

Go to subdirectory gladiwashere-java-mysql.

Reverse proxy

From a user perspective, the technology used to implement a particular application that runs on UBOS is totally irrelevant. We cannot require the user to access, say, Apps implemented in Java at a different port number than other Apps installed on the same device, because this makes no sense to the user.

Because of that, Java Apps on UBOS are usually configured with Apache as a reverse proxy in front of the application server. Apache takes incoming requests at port 80 or 443, and forwards them to Tomcat. This is what this example App does as well.

Package lifecycle and App deployment

Like all other Apps on UBOS including Hello World, this example App is built with makepkg, installed with pacman and deployed with ubos-admin.

% makepkg -f -s
% sudo pacman -U gladiwashere-java-mysql-*-any.pkg.tar.xz
% sudo ubos-admin createsite

Specify gladiwashere-java-mysql as the name of the App.

For the makepkg command here, we also specify option -s, which instructs makepkg to install dependencies needed for the build; in this case, a Java compiler and the maven build tool. They are given in the makedepends line in the PKGBUILD file.

Manifest JSON

Let’s examine this App’s UBOS Manifest file. It is very similar to the of gladiwashere-php-mysql, but has an additional role entry for Tomcat:

    "type" : "app",

    "roles" : {
        "apache2" : {
            "defaultcontext" : "/guestbook",
            "apache2modules" : [
            "appconfigitems" : [
                    "type" : "file",
                    "name" : "${appconfig.apache2.appconfigfragmentfile}",
                    "template"     : "tmpl/htaccess.tmpl",
                    "templatelang" : "varsubst"
        "tomcat8" : {
            "defaultcontext" : "/guestbook",
            "appconfigitems" : [
                    "type"         : "file",
                    "name"         : "${appconfig.tomcat8.contextfile}",
                    "template"     : "tmpl/context.xml.tmpl",
                    "templatelang" : "varsubst"
        "mysql" : {
            "appconfigitems" : [
                    "type"             : "database",
                    "name"             : "maindb",
                    "retentionpolicy"  : "keep",
                    "retentionbucket"  : "maindb",
                    "privileges"       : "select, insert"
            "installers" : [
                    "name"   : "maindb",
                    "type"   : "sqlscript",
                    "source" : "sql/create.sql"

Let’s first note what is the same as in the PHP version:

  • The type is app for both, of course.

  • The defaultcontext is the same.

  • The entire mysql section is the same, including database permissions and database initialization.

Here are the differences:

  • Apache now needs to use modules proxy and proxy_ajp, which allow Apache to talk to Tomcat using the AJP protocol. Because there is no more PHP involved, the Apache PHP modules are not needed any more.

  • Instead of having the PHP files as appconfigitems, there is only one Apache configuration fragment file that configures Apache as a reverse proxy. This file is in the package as a template, so UBOS can correctly parameterize it for the particular AppConfiguration (see below).

  • There’s a new tomcat8 section which configures Tomcat. All that’s needed here is a Tomcat “context file”, which again is parameterized (see below).

Note that there are no commands required to install or start Tomcat; UBOS does this automatically when it notices that a Java App with a tomcat8 Role is about to be deployed.

Apache reverse proxy configuration

The Apache reverse proxy configuration is quite straightforward:

ProxyPass /robots.txt !
ProxyPass /favicon.ico !
ProxyPass /sitemap.xml !
ProxyPass /.well-known !
ProxyPass /_common !
ProxyPass /_errors !

ProxyPass ${appconfig.contextorslash} ajp://${appconfig.contextorslash}
ProxyPassReverse ${appconfig.contextorslash} ajp://${appconfig.contextorslash}

At deployment time, UBOS will replace the variables in this template and save the resulting file as .htaccess in the web server directory, such as:

ProxyPass /robots.txt !
ProxyPass /favicon.ico !
ProxyPass /sitemap.xml !
ProxyPass /.well-known !
ProxyPass /_common !
ProxyPass /_errors !

ProxyPass /guestbook ajp://
ProxyPassReverse /guestbook ajp://

The last two lines form the reverse proxy: everything below /guesbook will be sent over to Tomcat, and everything returned within the Tomcat URL namespace will be re-translated into the the URL namespace that the client sees. Apache requires both of those statements, see the Apache documentation.

The four lines at the beginning declare that robots.txt, favicon.ico, sitemap.xml and .well-known shall not be mapped to the Tomcat application if the application runs at the root of the Site. This allows the Site JSON entries for the content of those files generated by UBOS continue to be used.

Similarly, line 5 and 6 keep UBOS’ HTTP error pages instead of delegating them to the Java application. For example, if a user were to access a URL that does not exist, the UBOS 404 error page will be shown.

Tomcat context file

Tomcat also needs to be told which App to run, and which parameters to pass to it. This is accomplished with the following template:

<?xml version="1.0" encoding="UTF-8"?>
<Context path="${appconfig.context}"

  <Loader className="org.diet4j.tomcat.TomcatModuleLoader"

  <Resource auth="Container"
            password="${escapeDquote( appconfig.mysql.dbusercredential.maindb )}"

Upon deployment, UBOS will have replaced the variables, and provided it to Tomcat, for example:

<?xml version="1.0" encoding="UTF-8"?>
<Context path="/guestbook"

  <Loader className="org.diet4j.tomcat.TomcatModuleLoader"

  <Resource auth="Container"

For details on how to configure Tomcat, see the Tomcat documentation.

This App is now using the diet4j module management framework, so Java Apps on UBOS fit more nicely into UBOS package management. As a result, this Tomcat App uses the diet4j TomcatModuleLoader to load its code, instead of the default Tomcat loader.

Instead of a giant WAR containing all dependencies, diet4j allows this App to only ships its own code, and use other JARs are dependencies that are installed in /ubos/lib/java, where diet4j can find them and their dependent modules at run-time. See this line in the PKGBUILD file:

# Code
install -D -m0644 ${startdir}/maven/target/${pkgname}-${pkgver}.war \

which basically says: take the generated (thin) .war file, and put it into /ubos/lib/java/net/ubos/ubos-toyapps/gladiwashere-java-mysql/<version>/gladiwashere-java-mysql-<version>.war.