--- name: "linux" section: "1" platform: "linux" package: "user-mode-linux" version: "2.4.18.17um-1" release: "Debian 3.0 (Woody)" platforms: ["linux"] url: "https://new.carta.tech/linux" --- # linux(1) User-mode Linux ## NAME linux — User-mode Linux ## SYNOPSIS **linux** \[*options* ...\] ## DESCRIPTION This manual page briefly documents User-mode Linux. This manual page was written for the **Debian GNU/Linux** distribution because the original program does not have a manual page. ## OPTIONS - mem=*memory* This controls how much "physical" memory the kernel allocates for the system. The size is specified as a number followed by one of 'k', 'K', 'm', 'M', which have the obvious meanings. This is not related to the amount of memory in the physical machine. It can be more, and the excess, if it's ever used, will just be swapped out. - iomem=*name*,*file* Configure *file* as a named IO memory region named *name*. - gdb-pid=*pid* gdb-pid is used to attach an external debugger to UML. This may be an already-running gdb or a debugger-like process like strace. - debugtrace Causes the tracing thread to pause until it is attached by a debugger and continued. This is mostly for debugging crashes early during boot, and should be pretty much obsoleted by the debug switch. - honeypot This makes UML put process stacks in the same location as they are on the host, allowing expoits such as stack smashes to work against UML. - debug Starts up the kernel under the control of gdb. See the kernel debugging tutorial and the debugging session pages in the user-mode-linux-doc package for more information. - root=*file* This is actually used by the generic kernel in exactly the same way as in any other kernel. If you configure a number of block devices and want to boot off something other than ubd0, you would use something like "root=/dev/ubd5". - umid=*name* This is used to assign a unique identity to this UML machine This is used for naming the pid file and management console socket. - uml\_dir=*directory* The location to place the pid and umid files. - initrd=*file* This is used to boot UML from an initrd image. The argument is the name of the file containing the image. - jail Enables the protection of kernel memory from processes - con\[0-9\]\*=*description* Attach a console to a host channel. Examples of channels include ttys, ptys, pts terminals, xterms, and file descriptors. - tty This will make UML attach the device to the specified tty. If the tty that you specify is the slave end of a tty/pty pair, something else must have already opened the corresponding pty in order for this to work. **con1=tty:/dev/tty3** - pty This will cause UML to allocate a free host pty for the device. The pty will be announced in the boot log. You would attach to it via the corresponding tty. **con1=pty** - pts terminal This is similar to pty above, but the specified UML device will be attached to a free pts device on the host. Look at the boot log to see which one. **con1=pts** - xterm UML will run an xterm and the device will be attached to it. **con1=xterm** - file descriptors If you set up a file descriptor on the UML command line, you can attach a UML device to it. This is most commonly used to put the main console back on stdin and stdout after assigning all the other consoles to something else. **con0=fd:0,fd:1 con=xterm** - You can also specify different input and output channels for a device by putting a comma between them: **ssl3=tty:/dev/tty2,xterm**. See *Setting* *up Serial Lines and Consoles (link to URL file:/usr/share/doc/user-mode-linux-doc/input.html)* for a more information. - ssl\[0-9\]\*=*description* Attach a serial line to a host channel. The same options are supported as for consoles, described above. - fake\_ide Create ide0 entries that map onto ubd devices. - ubd\[0-7\]\[r\]\[s\]=file - **ubd0r=/tmp/debian-woody.ext2** - **ubd0rs=/tmp/debian-woody.ext2** - **ubd0=/tmp/chroot** - This is used to associate a device with a file or in the underlying filesystem. Usually, there is a filesystem in the file, but that's not required. Swap devices containing swap files can be specified like this. Also, a file which doesn't contain a filesystem can have its contents read in the virtual machine by running dd on the device. Appending an 'r' will cause that device to be mounted read-only. Appending an 's' tells UML to open the file using O\_SYNC (synchronous I/O). - As a special case, if a directory is specified instead of a file for the ubd0 device, the root filesystem will be mounted as a hostfs filesystem using the specified directory. - fakehd Change the ubd device name to "hd", allowing programs within UML to access UBD devices as if they were normal IDE disks. - eth\[0-9\]+=*transport*,*options* Configure a network device. Formats and examples follow (one for each configured transport). - eth\[0-9\]+=ethertap,*device*,*ethernet\_address*,*tap\_ip\_address* **eth0=ethertap,tap0,,192.168.0.1** - eth\[0-9\]+=tuntap,,*ethernet\_address*,*ip\_address* **eth0=tuntap,,fe:fd:0:0:0:1,192.168.0.1** - eth\[0-9\]+=daemon,*ethernet\_address*,*type*,*control\_socket*,*data\_socket* **eth0=daemon,unix,/tmp/uml.ctl,/tmp/uml.data** - eth\[0-9\]+=slip,*slip\_ip* **eth0=slip,192.168.0.1** - eth\[0-9\]+=mcast,*ethernet\_address*,*address*,*port*,*ttl* **eth0=mcast,,224.2.3.4:5555,3** - \--help Prints syntax information. - \--version Prints the version number of the kernel ## SEE ALSO The *UserModeLinux-HOWTO (link to URL file:/usr/share/doc/user-mode-linux-doc/UserModeLinux-HOWTO.html)* ## AUTHOR User-mode Linux was written by Jeff Dike and others. This manual page was written by Matt Zimmerman mdz@debian.org for the **Debian GNU/Linux** system, based on **linux --help** and the user-mode-linux website.