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System Configuration—JailsFreeBSD offers built-in virtualization features that cannot be found in most otheroperating systems. Jails let the system administrator create one or more isolatedenvironments on a host FreeBSD system to run different services and applications.There are many scenarios where jails can help improve the security and scalabilityof the system, which are discussed in this chapter. Jails also provide valuableopportunities for service providers to minimize their hardware expenses and getthe best out of their hardware by running multiple instances of FreeBSDoperating environment on the same hardware.In this chapter, we will look at the following:• Concept• Introduction• Setting up a jail• Configuring the host system• Starting the jail• Automatic startup• Shutting down and managing jails• Jail security and limitationsConceptThe concept of chroot environment has been in BSD-like operating systems since the4.2BSD version. Using the chroot(8) utility, the system administrator can changethe root directory from the point of view of the specific processes. This will make theapplication assume the specified directory as the root directory of the system. Systemadministrator needs to replicate the required directory hierarchy (for example, /etcor /lib) under the specified chroot directory in order to make the application work.