The zones facility in Solaris provides an isolated environment for running applications. Processes running in a zone are prevented from monitoring or interfering with other activity in the system. Access to other processes, network interfaces, file systems, devices, and inter-process communication facilities are restricted to prevent interaction between processes in different zones.

The privileges available within a zone are restricted to prevent operations with system-wide impact. See privileges(5).

You can configure and administer zones with the zoneadm(1M) and zonecfg(1M) utilities. You can specify the configuration details a zone, install file system contents including software packages into the zone, and manage the runtime state of the zone. You can use the zlogin(1) to run commands within an active zone. You can do this without logging in through a network-based login server such as in.rlogind(1M) or sshd(1M).

The autobooting of zones is enabled and disabled by the zones service, identified by the FMRI:

svc:/system/zones:default

See zoneadm(1M). Note that a zone has an autoboot property, which can be set to true (always autoboot). However, if the zones service is disabled, autoboot will not occur, regardless of the setting of the autoboot property for a given zone. See zonecfg(1M).

An alphanumeric name and numeric ID identify each active zone. Alphanumeric names are configured using the zonecfg(1M) utility. Numeric IDs are automatically assigned when the zone is booted. The zonename(1) utility reports the current zone name, and the zoneadm(1M) utility can be used to report the names and IDs of configured zones.

A zone can be in one of several states: CONFIGURED

DOWN

Processes running inside a zone (aside from the global zone) have restricted access to other processes. Only processes in the same zone are visible through /proc (see proc(4) or through system call interfaces that take process IDs such as kill(2) and priocntl(2). Attempts to access processes that exist in other zones (including the global zone) fail with the same error code that would be issued if the specified process did not exist.

Processes running within a non-global zone are restricted to a subset of privileges, in order to prevent one zone from being able to perform operations that might affect other zones. The set of privileges limits the capabilities of privileged users (such as the super-user or root user) within the zone. The list of privileges available within a zone can be displayed using the ppriv(1) utility. For more information about privileges, see privileges(5).

The set of devices available within a zone is restricted, to prevent a process in one zone from interfering with processes in other zones. For example, a process in a zone should not be able to modify kernel memory using /dev/kmem, or modify the contents of the root disk. Thus, by default, only a few pseudo devices considered safe for use within a zone are available. Additional devices can be made available within specific zones using the zonecfg(1M) utility.

The device and privilege restrictions have a number of effects on the utilities that can run in a non-global zone. For example, the eeprom(1M), prtdiag(1M), and prtconf(1M) utilities do not work in a zone since they rely on devices that are not normally available.

A zone may be assigned a brand when it is initially created. A branded zone is one whose software does not match that software found in the global zone. The software may include Solaris software configured or laid out differently, or it may include non-Solaris software. The particular collection of software is called a "brand" (see brands(5)). Once installed, a zone's brand may not be changed unless the zone is first uninstalled.

Each zone has its own section of the file system hierarchy, rooted at a directory known as the zone root. Processes inside the zone can access only files within that part of the hierarchy, that is, files that are located beneath the zone root. This prevents processes in one zone from corrupting or examining file system data associated with another zone. The chroot(1M) utility can be used within a zone, but can only restrict the process to a root path accessible within the zone.

In order to preserve file system space, sections of the file system can be mounted into one or more zones using the read-only option of the lofs(7FS) file system. This allows the same file system data to be shared in multiple zones, while preserving the security guarantees supplied by zones.

NFS and autofs mounts established within a zone are local to that zone; they cannot be accessed from other zones, including the global zone. The mounts are removed when the zone is halted or rebooted.

A zone has its own port number space for TCP, UDP, and SCTP applications and typically one or more separate IP addresses (but some configurations of Trusted Extensions share IP address(es) between zones).

For the IP layer (IP routing, ARP, IPsec, IP Filter, and so on) a zone can either share the configuration and state with the global zone (a shared-IP zone), or have its distinct IP layer configuration and state (an exclusive-IP zone).

If a zone is to be connected to the same datalink, that is, be on the same IP subnet or subnets as the global zone, then it is appropriate for the zone to use the shared IP instance.

If a zone needs to be isolated at the IP layer on the network, for instance being connected to different VLANs or different LANs than the global zone and other non-global zones, then for isolation reasons the zone should have its exclusive IP.

A shared-IP zone is prevented from doing certain things towards the network (such as changing its IP address or sending spoofed IP or Ethernet packets), but an exclusive-IP zone has more or less the same capabilities towards the network as a separate host that is connected to the same network interface. In particular, the superuser in such a zone can change its IP address and spoof ARP packets.

The shared-IP zones are assigned one or more network interface names and IP addresses in zonecfg(1M). The network interface name(s) must also be configured in the global zone.

The exclusive-IP zones are assigned one or more network interface names in zonecfg(1M). The network interface names must be exclusively assigned to that zone, that is, it (or they) can not be assigned to some other running zone, nor can they be used by the global zone.

The full IP-level functionality in the form of DHCP client, IPsec and IP Filter, is available in exclusive-IP zones and not in shared-IP zones.

A zone is capable of emulating a 32-bit host identifier, which can be configured via zonecfg(1M), for the purpose of system consolidation. If a zone emulates a host identifier, then commands such as hostid(1) and sysdef(1M) as well as C interfaces such as sysinfo(2) and gethostid(3C) that are executed within the context of the zone will display or return the zone's emulated host identifier rather than the host machine's identifier.

hostid(1), zlogin(1), zonename(1), in.rlogind(1M), sshd(1M), sysdef(1M), zoneadm(1M), zonecfg(1M), kill(2), priocntl(2), sysinfo(2), gethostid(3C), getzoneid(3C), ucred_get(3C), proc(4), attributes(5), brands(5), privileges(5), crgetzoneid(9F)