Jail task Driver

Name: jail-task-driver

The Jail task driver provides an interface for using FreeBSD jails for running application containers. You can download the external jail-task-driver here. For more detailed instructions on how to set up and use this driver, please refer to the guide.

Task Configuration

task "http-echo-jail" {
        driver = "jail-task-driver"
        config {
            Path  = "/zroot/iocage/jails/myjail/root"
            Allow_raw_sockets = true
            Allow_chflags     = true
            Ip4_addr          = "em1|"
            Exec_start        = "/usr/local/bin/http-echo -listen :9999 -text hello"
            Rctl =  {
                Vmemoryuse = {
                    Action = "deny"
                    Amount = "1G"
                    Per = "process"
                Openfiles = {
                    Action = "deny"
                    Amount = "500"

The Jail task driver supports most of JAIL(8) parameters, for a list of the currently supported parameters, please refer to the Parameter Documentation.

  • Path - (Optional) The directory which is to be the root of the jail. Defaults to nomad's allocation directory.

  • Ip4 - (Optional) Control the availability of IPv4 addresses. Possible values are "inherit" to allow unrestricted access to all system addresses, "new" to restrict addresses via Ip4_addr, and "disable" to stop the jail from using IPv4 entirely.

  • Ip4_addr - (Optional) A list of IPv4 addresses assigned to the jail. If this is set, the jail is restricted to using only these addresses. Any attempts to use other addresses fail, and attempts to use wildcard addresses silently use the jailed address instead. For IPv4 the first address given will be used as the source address when source address selection on unbound sockets cannot find a better match. It is only possible to start multiple jails with the same IP address if none of the jails has more than this single overlapping IP address assigned to itself.

  • Allow_raw_sockets - (Optional) The jail root is allowed to create raw sockets. Setting this parameter allows utilities like ping(8) and traceroute(8) to operate inside the jail. If this is set, the source IP addresses are enforced to comply with the IP address bound to the jail, regardless of whether or not the IP_HDRINCL flag has been set on the socket. Since raw sockets can be used to configure and interact with various network subsystems, extra caution should be used where privileged access to jails is given out to untrusted parties.

Resource Isolation

Resource isolation on jails is enforced by RCTL(8) all parameters for resource control are supported.

  • Rctl - (Optional) Set resource limits on the jail, for a list of currently supported parameters, please refer to the Parameter Documentation.

        * `Vmemoryuse`   - (Optional) Address space limit,in bytes
        * `Cputime`      - (Optional) CPU time, in seconds
        * `Datasize`     - (Optional)  data size, in bytes
        * `Stacksize`    - (Optional   stack size, in bytes
        * `Coredumpsize` - (Optional)      core dump size, in bytes
        * `Memoryuse`    - (Optional)      resident set size, in bytes
        * `Memorylocked` - (Optional)      locked memory, in bytes
        * `Maxproc`      - (Optional)          number of processes
        * `Openfiles`    - (Optional)      file descriptor table size
        * `Vmemoryuse`   - (Optional)      address space limit,in bytes
        * `Pseudoterminals`  - (Optional)      number of PTYs
        * `Swapuse`  - (Optional)          swap space that may be reserved or used, in bytes
        * `Nthr`  - (Optional)         number of threads
        * `Msgqqueued`  - (Optional)       number of queued SysV messages
        * `Msgqsize`  - (Optional)     SysV message queue size, in bytes
        * `Nmsgq`  - (Optional)        number of SysV message queues
        * `Nsem`  - (Optional)         number of SysV semaphores
        * `Nsemop`  - (Optional)           number of SysV semaphores modified in a single semop(2) call
        * `Nshm`  - (Optional)         number of SysV shared memory segments
        * `Shmsize`  - (Optional)          SysV shared memory size, in bytes
        * `Wallclock`  - (Optional)    wallclock time, in seconds
        * `Pcpu`  - (Optional)         %CPU, in percents of a single CPU core
        * `Readbps`  - (Optional)          filesystem reads, in bytes per second
        * `Writebps`  - (Optional)     filesystem writes, in bytes per second
        * `Readiops`  - (Optional)     filesystem reads, in operations per second
        * `Writeiops`  - (Optional)    filesystem writes, in operations per second


The job spec could specify the Ip4addr parameter to add the jail's ip address to an specific interface at jail startup or the Vnet parameter to create a virtual network stack. Please refer to JAIL(8) for more details.

  • vnet jail - Example taken from Lucas, Michael W. FreeBSD Mastery: Jails (IT Mastery Book 15).
 task "test01" {
      driver = "jail-task-driver"
      config {
        Path    = "/zroot/iocage/jails/myjail/root"
        Host_hostname = "nomad00"
        Exec_clean = true
        Exec_start = "sh /etc/rc"
        Exec_stop = "sh /etc/rc.shutdown"
        Mount_devfs = true
        Exec_prestart = "logger trying to start "
        Exec_poststart = "logger jail has started"
        Exec_prestop = "logger shutting down jail "
        Exec_poststop = "logger has shut down jail "
        Exec_consolelog ="/var/tmp/vnet-example"
        Vnet = true
        Vnet_nic = "e0b_loghost"
        Exec_prestart = "/usr/share/examples/jails/jib addm loghost em1"
        Exec_poststop = "/usr/share/examples/jails/jib destroy loghost "

Client Requirements

jail-task-driver requires the following:

  • 64-bit FreeBSD 12.0-RELEASE host
  • The FreeBSD's Nomad binary
  • The jail-task-driver binary placed in the plugin_dir directory.
  • If resource control is going be used then RACCT must be enabled