# SPDX-License-Identifier: GPL-2.0 menu "UML Character Devices" config STDERR_CONSOLE bool "stderr console" default y help console driver which dumps all printk messages to stderr. config SSL bool "Virtual serial line" help The User-Mode Linux environment allows you to create virtual serial lines on the UML that are usually made to show up on the host as ttys or ptys. See for more information and command line examples of how to use this facility. Unless you have a specific reason for disabling this, say Y. config NULL_CHAN bool "null channel support" help This option enables support for attaching UML consoles and serial lines to a device similar to /dev/null. Data written to it disappears and there is never any data to be read. config PORT_CHAN bool "port channel support" help This option enables support for attaching UML consoles and serial lines to host portals. They may be accessed with 'telnet '. Any number of consoles and serial lines may be attached to a single portal, although what UML device you get when you telnet to that portal will be unpredictable. It is safe to say 'Y' here. config PTY_CHAN bool "pty channel support" help This option enables support for attaching UML consoles and serial lines to host pseudo-terminals. Access to both traditional pseudo-terminals (/dev/pty*) and pts pseudo-terminals are controlled with this option. The assignment of UML devices to host devices will be announced in the kernel message log. It is safe to say 'Y' here. config TTY_CHAN bool "tty channel support" help This option enables support for attaching UML consoles and serial lines to host terminals. Access to both virtual consoles (/dev/tty*) and the slave side of pseudo-terminals (/dev/ttyp* and /dev/pts/*) are controlled by this option. It is safe to say 'Y' here. config XTERM_CHAN bool "xterm channel support" help This option enables support for attaching UML consoles and serial lines to xterms. Each UML device so assigned will be brought up in its own xterm. It is safe to say 'Y' here. config NOCONFIG_CHAN bool default !(XTERM_CHAN && TTY_CHAN && PTY_CHAN && PORT_CHAN && NULL_CHAN) config CON_ZERO_CHAN string "Default main console channel initialization" default "fd:0,fd:1" help This is the string describing the channel to which the main console will be attached by default. This value can be overridden from the command line. The default value is "fd:0,fd:1", which attaches the main console to stdin and stdout. It is safe to leave this unchanged. config CON_CHAN string "Default console channel initialization" default "xterm" help This is the string describing the channel to which all consoles except the main console will be attached by default. This value can be overridden from the command line. The default value is "xterm", which brings them up in xterms. It is safe to leave this unchanged, although you may wish to change this if you expect the UML that you build to be run in environments which don't have X or xterm available. config SSL_CHAN string "Default serial line channel initialization" default "pty" help This is the string describing the channel to which the serial lines will be attached by default. This value can be overridden from the command line. The default value is "pty", which attaches them to traditional pseudo-terminals. It is safe to leave this unchanged, although you may wish to change this if you expect the UML that you build to be run in environments which don't have a set of /dev/pty* devices. config UML_SOUND tristate "Sound support" depends on SOUND select SOUND_OSS_CORE help This option enables UML sound support. If enabled, it will pull in the UML hostaudio relay, which acts as a intermediary between the host's dsp and mixer devices and the UML sound system. It is safe to say 'Y' here. endmenu menu "UML Network Devices" depends on NET # UML virtual driver config UML_NET bool "Virtual network device" help While the User-Mode port cannot directly talk to any physical hardware devices, this choice and the following transport options provide one or more virtual network devices through which the UML kernels can talk to each other, the host, and with the host's help, machines on the outside world. For more information, including explanations of the networking and sample configurations, see . If you'd like to be able to enable networking in the User-Mode linux environment, say Y; otherwise say N. Note that you must enable at least one of the following transport options to actually make use of UML networking. config UML_NET_ETHERTAP bool "Ethertap transport" depends on UML_NET help The Ethertap User-Mode Linux network transport allows a single running UML to exchange packets with its host over one of the host's Ethertap devices, such as /dev/tap0. Additional running UMLs can use additional Ethertap devices, one per running UML. While the UML believes it's on a (multi-device, broadcast) virtual Ethernet network, it's in fact communicating over a point-to-point link with the host. To use this, your host kernel must have support for Ethertap devices. Also, if your host kernel is 2.4.x, it must have CONFIG_NETLINK_DEV configured as Y or M. For more information, see That site has examples of the UML command line to use to enable Ethertap networking. If you'd like to set up an IP network with the host and/or the outside world, say Y to this, the Daemon Transport and/or the Slip Transport. You'll need at least one of them, but may choose more than one without conflict. If you don't need UML networking, say N. config UML_NET_TUNTAP bool "TUN/TAP transport" depends on UML_NET help The UML TUN/TAP network transport allows a UML instance to exchange packets with the host over a TUN/TAP device. This option will only work with a 2.4 host, unless you've applied the TUN/TAP patch to your 2.2 host kernel. To use this transport, your host kernel must have support for TUN/TAP devices, either built-in or as a module. config UML_NET_SLIP bool "SLIP transport" depends on UML_NET help The slip User-Mode Linux network transport allows a running UML to network with its host over a point-to-point link. Unlike Ethertap, which can carry any Ethernet frame (and hence even non-IP packets), the slip transport can only carry IP packets. To use this, your host must support slip devices. For more information, see . has examples of the UML command line to use to enable slip networking, and details of a few quirks with it. The Ethertap Transport is preferred over slip because of its limitations. If you prefer slip, however, say Y here. Otherwise choose the Multicast transport (to network multiple UMLs on multiple hosts), Ethertap (to network with the host and the outside world), and/or the Daemon transport (to network multiple UMLs on a single host). You may choose more than one without conflict. If you don't need UML networking, say N. config UML_NET_DAEMON bool "Daemon transport" depends on UML_NET help This User-Mode Linux network transport allows one or more running UMLs on a single host to communicate with each other, but not to the host. To use this form of networking, you'll need to run the UML networking daemon on the host. For more information, see That site has examples of the UML command line to use to enable Daemon networking. If you'd like to set up a network with other UMLs on a single host, say Y. If you need a network between UMLs on multiple physical hosts, choose the Multicast Transport. To set up a network with the host and/or other IP machines, say Y to the Ethertap or Slip transports. You'll need at least one of them, but may choose more than one without conflict. If you don't need UML networking, say N. config UML_NET_VECTOR bool "Vector I/O high performance network devices" depends on UML_NET help This User-Mode Linux network driver uses multi-message send and receive functions. The host running the UML guest must have a linux kernel version above 3.0 and a libc version > 2.13. This driver provides tap, raw, gre and l2tpv3 network transports with up to 4 times higher network throughput than the UML network drivers. config UML_NET_VDE bool "VDE transport" depends on UML_NET help This User-Mode Linux network transport allows one or more running UMLs on a single host to communicate with each other and also with the rest of the world using Virtual Distributed Ethernet, an improved fork of uml_switch. You must have libvdeplug installed in order to build the vde transport into UML. To use this form of networking, you will need to run vde_switch on the host. For more information, see That site has a good overview of what VDE is and also examples of the UML command line to use to enable VDE networking. If you need UML networking with VDE, say Y. config UML_NET_MCAST bool "Multicast transport" depends on UML_NET help This Multicast User-Mode Linux network transport allows multiple UMLs (even ones running on different host machines!) to talk to each other over a virtual ethernet network. However, it requires at least one UML with one of the other transports to act as a bridge if any of them need to be able to talk to their hosts or any other IP machines. To use this, your host kernel(s) must support IP Multicasting. For more information, see That site has examples of the UML command line to use to enable Multicast networking, and notes about the security of this approach. If you need UMLs on multiple physical hosts to communicate as if they shared an Ethernet network, say Y. If you need to communicate with other IP machines, make sure you select one of the other transports (possibly in addition to Multicast; they're not exclusive). If you don't need to network UMLs say N to each of the transports. config UML_NET_PCAP bool "pcap transport" depends on UML_NET help The pcap transport makes a pcap packet stream on the host look like an ethernet device inside UML. This is useful for making UML act as a network monitor for the host. You must have libcap installed in order to build the pcap transport into UML. For more information, see That site has examples of the UML command line to use to enable this option. If you intend to use UML as a network monitor for the host, say Y here. Otherwise, say N. config UML_NET_SLIRP bool "SLiRP transport" depends on UML_NET help The SLiRP User-Mode Linux network transport allows a running UML to network by invoking a program that can handle SLIP encapsulated packets. This is commonly (but not limited to) the application known as SLiRP, a program that can re-socket IP packets back onto he host on which it is run. Only IP packets are supported, unlike other network transports that can handle all Ethernet frames. In general, slirp allows the UML the same IP connectivity to the outside world that the host user is permitted, and unlike other transports, SLiRP works without the need of root level privleges, setuid binaries, or SLIP devices on the host. This also means not every type of connection is possible, but most situations can be accommodated with carefully crafted slirp commands that can be passed along as part of the network device's setup string. The effect of this transport on the UML is similar that of a host behind a firewall that masquerades all network connections passing through it (but is less secure). To use this you should first have slirp compiled somewhere accessible on the host, and have read its documentation. If you don't need UML networking, say N. Startup example: "eth0=slirp,FE:FD:01:02:03:04,/usr/local/bin/slirp" endmenu