How do I enable quotas on my RedHat server with no control panel?

As the root user, edit file /etc/fstab to add qualifier "usrquota" or "grpquota" to the partition you want quotas enabled for as shown below:
/dev/hda2 /home ext3 defaults,usrquota,grpquota 1 1


This enables user and group quotas support on the /home file system.
You can finish initializing quota support by simply rebooting your server. If a reboot isn't a viable option at the moment, you can also follow the instructions listed below:
1. Remount changed filesystems
To remount a specific filesystem: mount -o remount (ex. mount -o remount /dev/hda2)
2. Create aquota.user and aquota.group for quota accounting.
To create the aquota.user and aquota.group files which keep track of quotas, run the following command:
quotacheck -vguma
This command may take awhile to run as it scans any quota enabled filesystems to build the quota accounting files.
3. Enable quota account process.
To enable the quota accounting process which keeps tabs on user/group usage activity as it occurs and updates the aquota.user and aquota.group files, run this command:
quotaon -av
Your linux filesystem(s) should now be quota-enabled.

Your linux filesystem(s) is now quota enabled.