Updated: 29 September 2026 · Applies to: Apache Solr 10.0 with Java 21 on cPanel & WHM servers and other AlmaLinux, Rocky Linux and RHEL 9 and 10 servers
Apache Solr is an open-source search server built on Lucene. Shops, content management systems and site-search plugins use it for fast full-text search. cPanel does not manage Solr, but you can run it on the same server as a separate service. The old instructions for Solr 6 and Java 8 are long out of date. We installed Solr 10.0.0 with Java 21 on AlmaLinux 9 using the steps below.
Before you start
- Check which Solr version your application supports. Some need an older major version (for example Solr 9), and the steps are the same apart from the version number and Java version (Solr 9 needs Java 11 or later, Solr 10 needs Java 21).
- Solr needs memory of its own. Plan at least 1 GB for a small index, on top of what your websites use.
1. Install Java 21
dnf install java-21-openjdk-headless lsof java -version
2. Download and verify Solr
Get the current version from the Solr downloads page. The "slim" package leaves out optional modules and is enough for most sites:
cd /usr/local/src curl -O https://dlcdn.apache.org/solr/solr/10.0.0/solr-10.0.0-slim.tgz curl -O https://downloads.apache.org/solr/solr/10.0.0/solr-10.0.0-slim.tgz.sha512 sha512sum -c solr-10.0.0-slim.tgz.sha512
The last command must print OK.
3. Install Solr as a service
tar xzf solr-10.0.0-slim.tgz solr-10.0.0-slim/bin/install_solr_service.sh --strip-components=2 bash install_solr_service.sh solr-10.0.0-slim.tgz
The script creates a solr user, installs Solr in /opt/solr (a link to the versioned folder), keeps data and logs in /var/solr, writes the settings file /etc/default/solr.in.sh, and creates and starts the solr systemd service. If it stops with "Unable to auto-detect your *NIX distribution", install Solr manually as described in the Solr guide's "Taking Solr to Production" chapter.
4. Check that it runs, and only locally
systemctl status solr ss -ltn | grep 8983 curl -s http://127.0.0.1:8983/api/node/system | head
Solr listens only on 127.0.0.1 by default (SOLR_HOST_BIND in /etc/default/solr.in.sh), which is right when your websites on the same server use it. Do not open port 8983 in the firewall: Solr's admin interface has no login by default.
5. Create an index for your application
sudo -u solr /opt/solr/bin/solr create -c mysite
Solr 10 starts in SolrCloud mode by default, so this creates a "collection". Point your application to http://127.0.0.1:8983/solr/mysite. Many applications ship their own Solr configuration; follow their instructions to use it instead of the default.
Memory
Set the Java heap in /etc/default/solr.in.sh, for example SOLR_HEAP="1g", then systemctl restart solr. Keep it well below the server's free memory.
Official documentation: Solr: taking Solr to production and Solr downloads.
