If you've ever set up a Ruby on Rails application on a VPS running CentOS 7, you've likely encountered a range of installation challenges. One particularly common issue is when running bundle install
fails to install the pg
gem, which is essential for Rails applications that use PostgreSQL. Let’s go through this issue and the solution step-by-step.
The Problem
When running bundle install
on a CentOS 7 VPS, you may encounter an error similar to the following:
This error usually points to missing PostgreSQL development libraries or an incorrect path to the PostgreSQL configuration file pg_config
.
Why This Happens
The pg
gem requires access to PostgreSQL’s development files during installation. Specifically, it looks for pg_config
, a tool that provides information about PostgreSQL installation paths. Without it, the gem can't find necessary files such as libpq-fe.h
. The error is often caused by one of the following:
- PostgreSQL development headers (
postgresql-devel
) are missing. - The system doesn’t know where to find
pg_config
. pg_config
exists, but it’s not in the system’s PATH.
Solution
Let’s tackle this issue in three steps:
Confirm PostgreSQL Packages Are Installed
Make sure you have the necessary PostgreSQL development libraries installed. Run:
This should install the required headers and libraries for PostgreSQL 9.4. Adjust the version number based on the PostgreSQL version you are using.
Install the
pg
Gem with Configuration OptionsIf
pg_config
isn't in the system’s PATH, you need to provide its full path manually when installing thepg
gem. On CentOS,pg_config
is typically located in/usr/pgsql-9.4/bin/pg_config
. You can install thepg
gem directly using:This should allow the gem to find the necessary PostgreSQL files.
Automate the Process with Capistrano
If you’re using Capistrano for deployments, manually setting the
pg_config
path every time isn’t efficient. To streamline deployments, create a Capistrano task that configures Bundler to use the correct path forpg_config
automatically.Add the following task to your
deploy.rb
file:This task will create a
./bundle/config
file for your project and add thepg_config
path to thebuild.pg
configuration. By setting it beforebundler:install
, you ensure Bundler uses the correctpg_config
path during each deployment.Update the System’s PATH (Optional)
Another way to resolve this is by adding the
pg_config
directory to your system’s PATH. This way, you don’t have to specify the full path every time. Create a symbolic link to the PostgreSQL binaries with:After creating this link, your system should recognize
pg_config
globally, eliminating the need for the--with-pg-config
option.Verify Installation
Run
bundle install
again to ensure thepg
gem installs successfully. If everything is set up correctly, Bundler should be able to locatepg_config
and install the gem without issues.
Common Pitfalls
- Outdated PostgreSQL Version: Make sure the version of PostgreSQL you’re using matches the development packages installed on your system. If you’re using PostgreSQL 9.6, for example, make sure to install
postgresql96-devel
instead ofpostgresql94-devel
. - Multiple PostgreSQL Versions: Having multiple versions of PostgreSQL installed can confuse the
pg
gem installation. Ensure that only one version is in your PATH or specify the exact path topg_config
for the version you intend to use. - User Permissions: Make sure you’re running the commands as a user with sufficient permissions (usually
sudo
is required for installations and system-wide changes).
Conclusion
Installing the pg
gem on CentOS 7 can be a bit tricky, especially when PostgreSQL headers and libraries aren’t readily available in the PATH. By ensuring the PostgreSQL development packages are installed and that pg_config
is accessible, you can avoid these issues. Automating the configuration with Capistrano also simplifies the deployment process.
If you’ve followed these steps and are still encountering issues, double-check your installation paths and environment variables. With this setup, you should be able to successfully deploy your Rails application with PostgreSQL support on a CentOS 7 VPS.
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