Creating FreeBSD Jails

Prerequisites

# Ensure ZFS is available (recommended)
zpool list

# Create jail dataset
zfs create -o mountpoint=/jails zroot/jails

Method 1: bsdinstall

# Create jail root directory
mkdir -p /jails/myjail

# Run bsdinstall to install base system
bsdinstall jail /jails/myjail

# Follow prompts to select components

Method 2: Manual with fetch

# Download base system
fetch https://download.freebsd.org/releases/amd64/14.0-RELEASE/base.txz

# Extract to jail directory
mkdir -p /jails/myjail
tar -xf base.txz -C /jails/myjail

# Copy resolv.conf
cp /etc/resolv.conf /jails/myjail/etc/

Configure /etc/jail.conf

# /etc/jail.conf

# Global settings
exec.start = "/bin/sh /etc/rc";
exec.stop = "/bin/sh /etc/rc.shutdown";
exec.clean;
mount.devfs;

# Allow ping
allow.raw_sockets;

# Individual jail
myjail {
    host.hostname = "myjail.local";
    path = "/jails/myjail";

    # Networking (shared IP)
    ip4.addr = "em0|192.168.1.50/24";

    # Or use VNET
    # vnet;
    # vnet.interface = "epair0b";
}

Start the Jail

# Start jail
service jail start myjail

# Or manually
jail -c myjail

# List running jails
jls

# Enter jail
jexec myjail /bin/sh

Initial Jail Setup

# Inside the jail
jexec myjail /bin/sh

# Set root password
passwd

# Update pkg
pkg update && pkg upgrade

# Set timezone
tzsetup

# Enable sshd (if needed)
sysrc sshd_enable="YES"
service sshd start

Enable Jail at Boot

# In /etc/rc.conf
jail_enable="YES"
jail_list="myjail"

# Start all jails
service jail start

# Stop all jails
service jail stop

Thin Jails (Shared Base)

# Create base template
mkdir -p /jails/templates/base
tar -xf base.txz -C /jails/templates/base

# Create jail skeleton
mkdir -p /jails/templates/skeleton
mkdir -p /jails/templates/skeleton/{etc,home,root,usr/local,var}

# Create thin jail
mkdir -p /jails/thinjail

# Mount base read-only
mount -t nullfs -o ro /jails/templates/base /jails/thinjail

# Mount skeleton read-write
mount -t nullfs /jails/templates/skeleton /jails/thinjail/skeleton