How to Limit User Resources

Prerequisites

Before limiting user resources, make sure you have:

• SSH access to your VPS
• Root or sudo privileges

Method 1: Using /etc/security/limits.conf

Connect to your VPS:

ssh hxroot@YOUR_SERVER_IP -p 22

sudo nano /etc/security/limits.conf

Add limits for a user (e.g., "alice"):

alice        soft    nproc           10
alice        hard    nproc           20
alice        soft    nofile          100
alice        hard    nofile          200
alice        soft    core            0
alice        hard    core            0
alice        soft    cpu             60
alice        hard    cpu             120

Limit types explained:

• nproc – Maximum number of processes
• nofile – Maximum open file handles
• core – Core dump file size (0 disables)
• cpu – CPU time in minutes
• as – Address space limit (memory)
• rss – Resident set size (physical memory)
• data – Data segment size
• fsize – Maximum file size

Apply Changes (Reboot or re-login)

User must log out and log back in for limits to take effect.

Method 2: Using systemd cgroups (Per Service)

Edit service override:

sudo systemctl edit myapp.service

Add:

[Service]
CPUQuota=50%
MemoryMax=512M
TasksMax=20

Reload and restart:

sudo systemctl daemon-reload
sudo systemctl restart myapp

Method 3: Using cgroups directly (Advanced)

Create a control group:

sudo cgcreate -g cpu,memory:/limitedgroup
sudo cgset -r cpu.cfs_quota_us=50000 limitedgroup
sudo cgset -r memory.limit_in_bytes=536870912 limitedgroup

Run a process in the group:

sudo cgexec -g cpu,memory:/limitedgroup mycommand

Check Current User Limits

ulimit -a

For a specific user (switch user first):

su - alice
ulimit -a

Set Limits for All Users (Global Defaults)

In /etc/security/limits.conf:

*        soft    nproc           50
*        hard    nproc           100
*        soft    nofile          256
*        hard    nofile          512

Limits for root User

Add a separate section for root (usually not limited).