# Increase ScyllaDB resource limits over systemd

**Topic: Increasing resource limits when ScyllaDB runs and is managed via systemd**

**Audience: ScyllaDB administrators**

## Issue

Updates to `/etc/security/limits.d/scylla.conf` do not have any effect. After a cluster rolling restart is completed, the ScyllaDB limits listed under `/proc/<PID>/limits` are still the same or lower than what has been configured.

## Root Cause

When running under systemd, ScyllaDB uses the resource limits set in `/lib/systemd/system/scylla-server.service`, such as **LimitNPROC** — the maximum number of processes allowed to run in parallel (defaults to 8096). Limits configured through `/etc/security/limits.d` do not apply to systemd services.

Even though ScyllaDB’s provided defaults are suitable for most workloads, there may be situations on which these values may need to be overridden.

## Solution

1. To override ScyllaDB limits on systemd, run:

```shell
sudo systemctl edit scylla-server.service
```

1. Within the opened text editor, add the following lines and adjust the parameters as needed, e.g.:

```shell
[Service]
LimitNPROC=16384
```

1. Restart ScyllaDB:

```shell
sudo systemctl restart scylla-server.service
```

This will create a configuration file named `override.conf` under the `/etc/systemd/system/scylla-server.service.d` folder. Whenever editing this file by hand manually, remember to run `sudo systemctl daemon-reload` before restarting ScyllaDB, so that systemd reloads the changes.

1. To check the updated limits allowed by the ScyllaDB process run:

```shell
cat /proc/$(pidof scylla)/limits
```

## References

* The Linux Kernel Documentation for /proc/sys/fs/\* <[https://www.kernel.org/doc/Documentation/sysctl/fs.txt](https://www.kernel.org/doc/Documentation/sysctl/fs.txt)>
* systemd.exec(5) manpage