Update Ruby by first identifying who owns the current installation, then install a compatible replacement beside it, test the application with the service account, and only afterward switch production traffic. Use APT for an APT-installed Ruby, rbenv for an rbenv installation, RVM for an RVM installation, and the same documented build process for a source installation. Do not overwrite /usr/bin/ruby or remove the old runtime before you have a rollback path.
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1. Identify the Ruby installation before changing anything
The command that updates Ruby depends on how Ruby was installed. A Debian or Ubuntu package, an rbenv-managed version, an RVM installation, and a hand-built runtime can all answer ruby -v differently while sharing the same server. Using the wrong updater can leave multiple Rubies on PATH, break Bundler, or cause the application service to run a different version from your login shell.
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Run these commands as the account that normally deploys the application, and save the output:
ruby -v
which ruby
command -v ruby
gem envThen inspect the application and its service definition:
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- Read
GemfileandGemfile.lockfor arubydeclaration, Bundler version, and dependency constraints. - Check deployment scripts for
rbenv,rvm, an absolute Ruby path, or package commands. - Inspect the systemd unit, container definition, process supervisor, or scheduled job that starts the application.
- Record the current Ruby path, selected version, gem path, service user, and working directory.
A path such as /usr/bin/ruby usually indicates a distribution package. A path containing /.rbenv/shims/ indicates that rbenv’s shims are selecting the executable. A path under an RVM tree indicates RVM. A custom prefix such as /opt/ruby-... generally means a manually managed build. Treat these as clues and confirm them against the package database, manager configuration, and service unit rather than guessing.
2. Choose a target Ruby that your application can support
The newest release is not automatically the right release for a Rails or other Ruby application. Choose a target that satisfies the application’s declared Ruby requirement and all native or framework dependencies. Check the lockfile and deployment documentation before installing anything.
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Ruby’s documentation index lists these lifecycle dates:
| Ruby line | End of support listed by Ruby documentation | Practical implication |
|---|---|---|
| 3.0 | April 2024 | Plan a migration; do not treat an unsupported line as a long-term security strategy. |
| 3.1 | April 2025 | Move to a supported line after confirming application compatibility. |
| 3.2 | April 2026 | As of October 2026, recheck your support and vendor policy before retaining it. |
Lifecycle dates can change as the Ruby project publishes updates, so verify the current status immediately before a production change. An Ubuntu or Debian package that remains on an older minor line may still be the correct supported package for that operating-system release; support for the OS package and upstream Ruby support are separate questions.
3. Select the update route
| Current installation | Use this route | Main trade-off |
|---|---|---|
| Debian or Ubuntu package | Refresh APT metadata and upgrade or install the Ruby package. | Integrates with operating-system updates, but the repository can lag the newest upstream Ruby. |
| Several applications need different versions | Use rbenv with ruby-build and a project .ruby-version. |
Per-project isolation; each version may need compiler and library dependencies. |
| Server already uses RVM | Install and select the replacement through RVM. | Preserves existing gemset and deployment behavior; the service account must load RVM. |
| Manual compilation or custom options | Rebuild from source with the same toolchain and versioned prefix. | Maximum control, but you own patching, rebuilds, and dependency maintenance. |
Do not mix methods casually. For example, installing an APT Ruby while expecting an rbenv shim to select it can produce a working interactive shell but a different production service. Keep one explicit ownership model for each application.
4. Update an APT-managed Ruby on Debian or Ubuntu
Inspect the candidate before installing
APT is the operating system’s supported interface for Debian packages. Refresh repository indexes and inspect which Ruby versions are available:
sudo apt update
apt-cache policy ruby ruby-fullReview the candidate version, repository origin, and whether an upgrade is available. If the candidate does not meet your application’s requirement, do not force a different package over the top; use an approved repository or a version manager according to your operating policy.
Apply the package update
sudo apt upgrade
sudo apt install ruby-full
ruby -v
which rubyapt upgrade applies available upgrades for installed packages. ruby-full installs the complete distribution package where that package is appropriate for the release. The exact Ruby version depends on the Debian or Ubuntu release and enabled repositories, so record the output rather than assuming it matches the upstream stable release.
Keep the package and service aligned
- Confirm that the service unit invokes the same Ruby path you just checked.
- Run the application’s dependency installation or verification under the new interpreter, using the deployment procedure already defined for the project.
- Do not delete or replace
/usr/bin/rubyby hand. Package-managed files must remain under package-manager control. - If a separate manager is present, document which one wins on
PATHfor both the deployment account and the service account.
5. Update with rbenv
rbenv is a Ruby version manager for Unix-like systems. Its shims intercept ruby, gem, and bundle, then select a version based on local, shell, or global configuration. The rbenv install command is supplied by the ruby-build plugin, so both components must be installed and maintained.
Install and select the replacement
rbenv install -l
rbenv install <target-version>
cd /srv/your-app
rbenv local <target-version>
ruby -v
which rubyrbenv install -l lists versions known to your ruby-build release. The install step compiles or installs the selected version and may require a compiler, development headers, and libraries for OpenSSL, readline, YAML, and other extensions. Install those prerequisites using your distribution’s documented packages, and capture them in configuration management so the build is repeatable.
rbenv local creates or updates .ruby-version in the application directory. That file makes the selection explicit for commands run from that directory. rbenv global changes the default for the user, but a project-local version is safer when one server hosts multiple applications.
Refresh gems without changing the lockfile accidentally
With the target selected, run the project’s normal Bundler procedure. Check the Bundler version recorded in the lockfile and use the deployment command that the application already expects. Avoid an unplanned dependency resolution while changing Ruby; update gems in a separate, reviewable change if the lockfile requires it.
Make the service load rbenv
Non-interactive systemd services do not automatically read the shell startup files that initialize rbenv. Configure the unit or its environment so the service uses the intended shims, or set an explicit absolute path to the selected Ruby and its Bundler. After editing the unit, reload it and verify from the service account, not only from your own shell.
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sudo systemctl restart your-app.service
sudo -u appuser -H bash -lc 'ruby -v; which ruby; gem env'Use the service’s actual user and unit name. If the command reports the system Ruby, the service has not loaded rbenv or its PATH is ordered incorrectly.
6. Update with RVM
If the server already uses RVM, keep the existing workflow. RVM manages Ruby installations, selection, and (where configured) gemsets. Replacing it with another manager during the same change makes diagnosis and rollback harder.
rvm list
rvm install <ruby-version>
rvm use <ruby-version> --default
ruby -v
which rubyRVM documents rvm install INTERPRETER[-VERSION] for installing a Ruby and rvm get stable for upgrading RVM itself. Upgrade RVM separately from the application Ruby unless a compatibility issue requires both changes. If the deployment uses a named gemset, select or create it according to the existing deployment script rather than silently installing gems into a different set.
RVM initialization is also account-specific. Ensure the service user loads the same RVM scripts and selects the same Ruby and gemset as the deployment account. Verify the resulting executable and gem environment under that user before restarting production traffic.
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7. Rebuild a source installation safely
Source compilation is appropriate when no suitable prebuilt package exists or when you need a specific build option. Ruby’s installation guidance presents it as the most flexible route, but it transfers responsibility for compiler versions, linked libraries, patching, and repeatability to you.
- Pin the exact Ruby source version and record the compiler, configure options, operating-system release, and library versions.
- Verify the downloaded source using your organization’s approved integrity and provenance procedure.
- Install into a new, versioned prefix such as
/opt/ruby/<version>; do not overwrite the prefix used by the running application. - Build and run the Ruby test suite or your established smoke checks.
- Point the application and service definition at the new prefix only after dependencies and application tests pass.
- Keep the previous prefix intact until the deployment has been accepted.
Versioned prefixes make rollback a path change instead of an emergency rebuild. Record the build recipe in configuration management so the same runtime can be reproduced on a replacement server.
8. Test the application before switching production
Installing Ruby is only the first half of the change. Native gems can need recompilation, and a successful ruby -v does not prove that Rails boots or that the service can reach its database.
- From the application directory, confirm the selected Ruby, Bundler, and gem paths.
- Run the project’s dependency check or installation command using the locked dependencies and the new interpreter.
- Run the complete automated test suite that is practical for the maintenance window, including tests for database adapters, background jobs, asset compilation, and native extensions used in production.
- Start a staging or canary process with the new Ruby and inspect startup logs for missing shared libraries, load errors, warnings treated as failures, and environment differences.
- Exercise a critical request path, a write operation, a background job, and any scheduled task that uses Ruby.
- Compare logs, response errors, memory behavior, and job throughput with the known-good deployment.
Use the same environment variables, working directory, service user, and filesystem permissions as production. Testing only from an administrator’s interactive shell can hide a missing manager initialization or a permission problem.
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9. Verify both the login shell and the service account
Ruby selection is often a PATH problem rather than an installation problem. rbenv shims, RVM initialization, shell startup files, systemd environment settings, and deployment wrappers can all select different executables.
Run equivalent checks in both contexts:
ruby -v
which ruby
command -v ruby
gem env
bundle -vFor a systemd service, use the service account and its non-interactive environment:
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sudo -u appuser -H bash -lc 'ruby -v; which ruby; command -v bundle; gem env'
sudo systemctl status your-app.service
sudo journalctl -u your-app.service -n 200 --no-pagerReplace appuser and your-app.service with the values from your unit. The expected Ruby path must be the one selected by your chosen ownership model. If the service and login shell differ, fix the unit or deployment environment before changing application code.
10. Switch, monitor, and keep a rollback path
Install the replacement beside the old runtime and retain the old selection until the new deployment is accepted. A rollback should restore the previous version choice and service configuration, not require downloading and compiling Ruby during an outage.
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- Record the previous Ruby version, executable path, manager settings, gemset, service unit revision, and lockfile revision.
- Deploy the tested application with the new Ruby and restart or reload the relevant service using the documented procedure.
- Immediately check service status, logs, health checks, error rates, critical requests, background jobs, and scheduled tasks.
- Keep the old Ruby installation and configuration available during the observation period required by your operations policy.
- If the new runtime fails, stop or drain the affected process, restore the previous version selection and service configuration, reload the service manager, and confirm the old runtime with the service-account checks.
- Investigate the failure before attempting another upgrade; do not remove the old runtime until the change is stable and the rollback window has closed.
For rbenv, rollback normally means restoring the prior .ruby-version and restarting the service. For RVM, select the previous Ruby and gemset. For APT, use the package version and repository policy approved for that operating-system release rather than manually replacing package files. For a source build, point the service back to the previous versioned prefix.
11. Security and maintenance after the update
Keep the Linux distribution within its supported window. Ubuntu states that supported releases receive security updates during that window, generally as backported patches, with coverage depending on the repository component. A backported security fix does not necessarily change the Ruby minor version shown by ruby -v.
- Apply normal operating-system security updates through the distribution’s package process.
- Track Ruby’s upstream release and end-of-support dates separately from the OS lifecycle.
- Rebuild or upgrade manager-installed Rubies when their linked libraries or compiler toolchain require it.
- Keep the Ruby version declaration, lockfile, build instructions, and service environment under version control.
- Schedule compatibility testing before the next Ruby line reaches the end of support.
12. Troubleshooting common failures
ruby -v still shows the old version
Check which ruby and command -v ruby. If the path is an rbenv shim, inspect the project’s .ruby-version, shell selection, and rbenv initialization. If it is /usr/bin/ruby, you may have updated a manager-controlled Ruby or a different user. Re-run the checks in the application directory and under the service account.
The shell uses the new Ruby but the service uses the old one
Inspect the service unit’s Environment, ExecStart, working directory, and service user. Non-interactive services do not necessarily load your shell profile. Set an explicit, documented environment or absolute Ruby path, run systemctl daemon-reload, restart the service, and verify with sudo -u.
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Update the ruby-build plugin through its documented method, confirm that the requested version is listed by rbenv install -l, and install the distribution’s required compiler and development libraries. Preserve the build output; it identifies missing headers and incompatible libraries. Do not change the production selector until a complete build succeeds.
Bundler cannot install a locked gem
Read the error in the context of the target Ruby and the lockfile. A gem may not support the selected Ruby, may require a native library, or may need a newer Bundler. Resolve the compatibility issue in a separate dependency change when possible, then regenerate and review the lockfile under version control. Avoid deleting the lockfile as a first response.
The application boots but fails on real traffic
Check production logs, database adapter behavior, background workers, scheduled jobs, and native extensions. Compare environment variables and filesystem permissions between the test shell and the service. Restore the prior runtime if the health checks or critical request path remain unhealthy, then investigate with the old version serving traffic.
Quick Recap
Practical pre-change checklist
- Current
ruby -v, executable path,gem env, and Bundler version recorded. - Installation owner identified as APT, rbenv, RVM, or a source build.
- Application Ruby requirement, lockfile, framework, and native dependencies reviewed.
- Target Ruby’s support status and the operating system’s package availability confirmed.
- Replacement installed beside the old runtime and build prerequisites documented.
- Tests and smoke checks passed with the same account and environment used by production.
- Service unit, service user, logs, health checks, and rollback selector verified.
- Old runtime retained until the observation and rollback window ends.
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