How to Manage Resources with systemd on Ubuntu?

Introduction

Managing system resources like CPU and memory is very important for maintaining a stable and efficient server. In Ubuntu, systemd resource management helps control how processes use these resources through a feature called cgroups (control groups). Two important components of this system are slices and scopes. These help organize processes and apply resource limits effectively.

In this blog, you will learn what slices and scopes are, and how to use them in a simple way.

Prerequisites

Before getting started, make sure you have:

• An Ubuntu OS
• Basic knowledge of Linux commands
• Sudo (administrator) access

Understanding Slices and Scopes

• Slices: They are used to group services together and apply shared resource limits like CPU and memory.
• Scopes: They are used to manage processes that are not started directly by systemd, such as manually executed commands.

In simple terms:

• Slices = Organizing and limiting services
• Scopes = Managing running processes

Steps to Use systemd Slices and Scopes

Step 1: View Current System Hierarchy

You can see how processes are organized using:

systemd-cgls
systemd-cgtop

Step 2: Create a Custom Slice

Create a new slice to group services:

sudo nano /etc/systemd/system/myfirst.slice

Add:

[Slice]
MemoryMax=2G
CPUQuota=200%
TasksMax=500

Reload systemd:

sudo systemctl daemon-reload
sudo systemctl start myfirst.slice

This sets limits for all services in the slice.

Step 3: Assign Services to the Slice

Edit your service file:

[Service]
Slice=myfirst.slice

Now multiple services will share the same resource limits.

Step 4: Create Nested Slices (Optional)

You can create parent and child slices to organize workloads. For example:

• app.slice
• app-web.slice
• app-workers.slice

Child slices inherit limits from parent slices.

Step 5: Use Scopes for Running Processes

Run a process inside a controlled scope:

sudo systemd-run --scope -p MemoryMax=512M -p CPUQuota=50% /path/to/app

This allows you to control resources for temporary processes.

Step 6: Monitor Resource Usage

Check usage with:

systemd-cgtop
systemctl status myfirst.slice

This helps track CPU and memory usage in real time.

Conclusion

systemd slices and scopes provide a useful way to manage system resources in Ubuntu. Slices help organize services into groups and apply shared limits, while scopes allow control of external processes. By using these features, we can ensure that important applications get enough resources and prevent others from consuming too much. We can build a more stable, efficient, and well-managed system with proper use of slices and scopes.

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