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| -rw-r--r-- | Documentation/virtual/uml/UserModeLinux-HOWTO.txt | 532 |
1 files changed, 266 insertions, 266 deletions
diff --git a/Documentation/virtual/uml/UserModeLinux-HOWTO.txt b/Documentation/virtual/uml/UserModeLinux-HOWTO.txt index 5d0fc8bfcdb..77dfecf4e2d 100644 --- a/Documentation/virtual/uml/UserModeLinux-HOWTO.txt +++ b/Documentation/virtual/uml/UserModeLinux-HOWTO.txt @@ -134,13 +134,13 @@ ______________________________________________________________________ - 11.. IInnttrroodduuccttiioonn + 1. Introduction Welcome to User Mode Linux. It's going to be fun. - 11..11.. HHooww iiss UUsseerr MMooddee LLiinnuuxx DDiiffffeerreenntt?? + 1.1. How is User Mode Linux Different? Normally, the Linux Kernel talks straight to your hardware (video card, keyboard, hard drives, etc), and any programs which run ask the @@ -181,7 +181,7 @@ - 11..22.. WWhhyy WWoouulldd II WWaanntt UUsseerr MMooddee LLiinnuuxx?? + 1.2. Why Would I Want User Mode Linux? 1. If User Mode Linux crashes, your host kernel is still fine. @@ -206,12 +206,12 @@ - 22.. CCoommppiilliinngg tthhee kkeerrnneell aanndd mmoodduulleess + 2. Compiling the kernel and modules - 22..11.. CCoommppiilliinngg tthhee kkeerrnneell + 2.1. Compiling the kernel Compiling the user mode kernel is just like compiling any other @@ -322,7 +322,7 @@ bug fixes and enhancements that have gone into subsequent releases. - 22..22.. CCoommppiilliinngg aanndd iinnssttaalllliinngg kkeerrnneell mmoodduulleess + 2.2. Compiling and installing kernel modules UML modules are built in the same way as the native kernel (with the exception of the 'ARCH=um' that you always need for UML): @@ -386,19 +386,19 @@ - 22..33.. CCoommppiilliinngg aanndd iinnssttaalllliinngg uummll__uuttiilliittiieess + 2.3. Compiling and installing uml_utilities Many features of the UML kernel require a user-space helper program, so a uml_utilities package is distributed separately from the kernel patch which provides these helpers. Included within this is: - +o port-helper - Used by consoles which connect to xterms or ports + o port-helper - Used by consoles which connect to xterms or ports - +o tunctl - Configuration tool to create and delete tap devices + o tunctl - Configuration tool to create and delete tap devices - +o uml_net - Setuid binary for automatic tap device configuration + o uml_net - Setuid binary for automatic tap device configuration - +o uml_switch - User-space virtual switch required for daemon + o uml_switch - User-space virtual switch required for daemon transport The uml_utilities tree is compiled with: @@ -423,11 +423,11 @@ - 33.. RRuunnnniinngg UUMMLL aanndd llooggggiinngg iinn + 3. Running UML and logging in - 33..11.. RRuunnnniinngg UUMMLL + 3.1. Running UML It runs on 2.2.15 or later, and all 2.4 kernels. @@ -454,7 +454,7 @@ - 33..22.. LLooggggiinngg iinn + 3.2. Logging in @@ -468,7 +468,7 @@ There are a couple of other ways to log in: - +o On a virtual console + o On a virtual console @@ -480,7 +480,7 @@ - +o Over the serial line + o Over the serial line In the boot output, find a line that looks like: @@ -503,7 +503,7 @@ - +o Over the net + o Over the net If the network is running, then you can telnet to the virtual @@ -514,13 +514,13 @@ down and the process will exit. - 33..33.. EExxaammpplleess + 3.3. Examples Here are some examples of UML in action: - +o A login session <http://user-mode-linux.sourceforge.net/login.html> + o A login session <http://user-mode-linux.sourceforge.net/login.html> - +o A virtual network <http://user-mode-linux.sourceforge.net/net.html> + o A virtual network <http://user-mode-linux.sourceforge.net/net.html> @@ -528,12 +528,12 @@ - 44.. UUMMLL oonn 22GG//22GG hhoossttss + 4. UML on 2G/2G hosts - 44..11.. IInnttrroodduuccttiioonn + 4.1. Introduction Most Linux machines are configured so that the kernel occupies the @@ -546,7 +546,7 @@ - 44..22.. TThhee pprroobblleemm + 4.2. The problem The prebuilt UML binaries on this site will not run on 2G/2G hosts @@ -558,7 +558,7 @@ - 44..33.. TThhee ssoolluuttiioonn + 4.3. The solution The fix for this is to rebuild UML from source after enabling @@ -576,7 +576,7 @@ - 55.. SSeettttiinngg uupp sseerriiaall lliinneess aanndd ccoonnssoolleess + 5. Setting up serial lines and consoles It is possible to attach UML serial lines and consoles to many types @@ -586,12 +586,12 @@ You can attach them to host ptys, ttys, file descriptors, and ports. This allows you to do things like - +o have a UML console appear on an unused host console, + o have a UML console appear on an unused host console, - +o hook two virtual machines together by having one attach to a pty + o hook two virtual machines together by having one attach to a pty and having the other attach to the corresponding tty - +o make a virtual machine accessible from the net by attaching a + o make a virtual machine accessible from the net by attaching a console to a port on the host. @@ -599,7 +599,7 @@ - 55..11.. SSppeecciiffyyiinngg tthhee ddeevviiccee + 5.1. Specifying the device Devices are specified with "con" or "ssl" (console or serial line, respectively), optionally with a device number if you are talking @@ -626,13 +626,13 @@ - 55..22.. SSppeecciiffyyiinngg tthhee cchhaannnneell + 5.2. Specifying the channel There are a number of different types of channels to attach a UML device to, each with a different way of specifying exactly what to attach to. - +o pseudo-terminals - device=pty pts terminals - device=pts + o pseudo-terminals - device=pty pts terminals - device=pts This will cause UML to allocate a free host pseudo-terminal for the @@ -640,20 +640,20 @@ log. You access it by attaching a terminal program to the corresponding tty: - +o screen /dev/pts/n + o screen /dev/pts/n - +o screen /dev/ttyxx + o screen /dev/ttyxx - +o minicom -o -p /dev/ttyxx - minicom seems not able to handle pts + o minicom -o -p /dev/ttyxx - minicom seems not able to handle pts devices - +o kermit - start it up, 'open' the device, then 'connect' + o kermit - start it up, 'open' the device, then 'connect' - +o terminals - device=tty:tty device file + o terminals - device=tty:tty device file This will make UML attach the device to the specified tty (i.e @@ -672,7 +672,7 @@ - +o xterms - device=xterm + o xterms - device=xterm UML will run an xterm and the device will be attached to it. @@ -681,7 +681,7 @@ - +o Port - device=port:port number + o Port - device=port:port number This will attach the UML devices to the specified host port. @@ -725,7 +725,7 @@ - +o already-existing file descriptors - device=file descriptor + o already-existing file descriptors - device=file descriptor If you set up a file descriptor on the UML command line, you can @@ -743,7 +743,7 @@ - +o Nothing - device=null + o Nothing - device=null This allows the device to be opened, in contrast to 'none', but @@ -754,7 +754,7 @@ - +o None - device=none + o None - device=none This causes the device to disappear. @@ -770,7 +770,7 @@ - will cause serial line 3 to accept input on the host's /dev/tty3 and + will cause serial line 3 to accept input on the host's /dev/tty2 and display output on an xterm. That's a silly example - the most common use of this syntax is to reattach the main console to stdin and stdout as shown above. @@ -785,7 +785,7 @@ - 55..33.. EExxaammpplleess + 5.3. Examples There are a number of interesting things you can do with this capability. @@ -838,7 +838,7 @@ prompt of the other virtual machine. - 66.. SSeettttiinngg uupp tthhee nneettwwoorrkk + 6. Setting up the network @@ -858,19 +858,19 @@ There are currently five transport types available for a UML virtual machine to exchange packets with other hosts: - +o ethertap + o ethertap - +o TUN/TAP + o TUN/TAP - +o Multicast + o Multicast - +o a switch daemon + o a switch daemon - +o slip + o slip - +o slirp + o slirp - +o pcap + o pcap The TUN/TAP, ethertap, slip, and slirp transports allow a UML instance to exchange packets with the host. They may be directed @@ -893,28 +893,28 @@ With so many host transports, which one should you use? Here's when you should use each one: - +o ethertap - if you want access to the host networking and it is + o ethertap - if you want access to the host networking and it is running 2.2 - +o TUN/TAP - if you want access to the host networking and it is + o TUN/TAP - if you want access to the host networking and it is running 2.4. Also, the TUN/TAP transport is able to use a preconfigured device, allowing it to avoid using the setuid uml_net helper, which is a security advantage. - +o Multicast - if you want a purely virtual network and you don't want + o Multicast - if you want a purely virtual network and you don't want to set up anything but the UML - +o a switch daemon - if you want a purely virtual network and you + o a switch daemon - if you want a purely virtual network and you don't mind running the daemon in order to get somewhat better performance - +o slip - there is no particular reason to run the slip backend unless + o slip - there is no particular reason to run the slip backend unless ethertap and TUN/TAP are just not available for some reason - +o slirp - if you don't have root access on the host to setup + o slirp - if you don't have root access on the host to setup networking, or if you don't want to allocate an IP to your UML - +o pcap - not much use for actual network connectivity, but great for + o pcap - not much use for actual network connectivity, but great for monitoring traffic on the host Ethertap is available on 2.4 and works fine. TUN/TAP is preferred @@ -926,7 +926,7 @@ exploit the helper's root privileges. - 66..11.. GGeenneerraall sseettuupp + 6.1. General setup First, you must have the virtual network enabled in your UML. If are running a prebuilt kernel from this site, everything is already @@ -995,7 +995,7 @@ - 66..22.. UUsseerrssppaaccee ddaaeemmoonnss + 6.2. Userspace daemons You will likely need the setuid helper, or the switch daemon, or both. They are both installed with the RPM and deb, so if you've installed @@ -1011,7 +1011,7 @@ - 66..33.. SSppeecciiffyyiinngg eetthheerrnneett aaddddrreesssseess + 6.3. Specifying ethernet addresses Below, you will see that the TUN/TAP, ethertap, and daemon interfaces allow you to specify hardware addresses for the virtual ethernet @@ -1023,11 +1023,11 @@ sufficient to guarantee a unique hardware address for the device. A couple of exceptions are: - +o Another set of virtual ethernet devices are on the same network and + o Another set of virtual ethernet devices are on the same network and they are assigned hardware addresses using a different scheme which may conflict with the UML IP address-based scheme - +o You aren't going to use the device for IP networking, so you don't + o You aren't going to use the device for IP networking, so you don't assign the device an IP address If you let the driver provide the hardware address, you should make @@ -1049,7 +1049,7 @@ - 66..44.. UUMMLL iinntteerrffaaccee sseettuupp + 6.4. UML interface setup Once the network devices have been described on the command line, you should boot UML and log in. @@ -1131,7 +1131,7 @@ - 66..55.. MMuullttiiccaasstt + 6.5. Multicast The simplest way to set up a virtual network between multiple UMLs is to use the mcast transport. This was written by Harald Welte and is @@ -1194,7 +1194,7 @@ - 66..66.. TTUUNN//TTAAPP wwiitthh tthhee uummll__nneett hheellppeerr + 6.6. TUN/TAP with the uml_net helper TUN/TAP is the preferred mechanism on 2.4 to exchange packets with the host. The TUN/TAP backend has been in UML since 2.4.9-3um. @@ -1247,10 +1247,10 @@ There are a couple potential problems with running the TUN/TAP transport on a 2.4 host kernel - +o TUN/TAP seems not to work on 2.4.3 and earlier. Upgrade the host + o TUN/TAP seems not to work on 2.4.3 and earlier. Upgrade the host kernel or use the ethertap transport. - +o With an upgraded kernel, TUN/TAP may fail with + o With an upgraded kernel, TUN/TAP may fail with File descriptor in bad state @@ -1269,7 +1269,7 @@ - 66..77.. TTUUNN//TTAAPP wwiitthh aa pprreeccoonnffiigguurreedd ttaapp ddeevviiccee + 6.7. TUN/TAP with a preconfigured tap device If you prefer not to have UML use uml_net (which is somewhat insecure), with UML 2.4.17-11, you can set up a TUN/TAP device @@ -1277,7 +1277,7 @@ there is no need for root assistance. Setting up the device is done as follows: - +o Create the device with tunctl (available from the UML utilities + o Create the device with tunctl (available from the UML utilities tarball) @@ -1291,7 +1291,7 @@ where uid is the user id or username that UML will be run as. This will tell you what device was created. - +o Configure the device IP (change IP addresses and device name to + o Configure the device IP (change IP addresses and device name to suit) @@ -1303,7 +1303,7 @@ - +o Set up routing and arping if desired - this is my recipe, there are + o Set up routing and arping if desired - this is my recipe, there are other ways of doing the same thing @@ -1338,7 +1338,7 @@ utility which reads the information from a config file and sets up devices at boot time. - +o Rather than using up two IPs and ARPing for one of them, you can + o Rather than using up two IPs and ARPing for one of them, you can also provide direct access to your LAN by the UML by using a bridge. @@ -1417,7 +1417,7 @@ Note that 'br0' should be setup using ifconfig with the existing IP address of eth0, as eth0 no longer has its own IP. - +o + o Also, the /dev/net/tun device must be writable by the user running @@ -1438,11 +1438,11 @@ devices and chgrp /dev/net/tun to that group with mode 664 or 660. - +o Once the device is set up, run UML with 'eth0=tuntap,device name' + o Once the device is set up, run UML with 'eth0=tuntap,device name' (i.e. 'eth0=tuntap,tap0') on the command line (or do it with the mconsole config command). - +o Bring the eth device up in UML and you're in business. + o Bring the eth device up in UML and you're in business. If you don't want that tap device any more, you can make it non- persistent with @@ -1465,7 +1465,7 @@ - 66..88.. EEtthheerrttaapp + 6.8. Ethertap Ethertap is the general mechanism on 2.2 for userspace processes to exchange packets with the kernel. @@ -1561,9 +1561,9 @@ - 66..99.. TThhee sswwiittcchh ddaaeemmoonn + 6.9. The switch daemon - NNoottee: This is the daemon formerly known as uml_router, but which was + Note: This is the daemon formerly known as uml_router, but which was renamed so the network weenies of the world would stop growling at me. @@ -1649,7 +1649,7 @@ - 66..1100.. SSlliipp + 6.10. Slip Slip is another, less general, mechanism for a process to communicate with the host networking. In contrast to the ethertap interface, @@ -1681,7 +1681,7 @@ - 66..1111.. SSlliirrpp + 6.11. Slirp slirp uses an external program, usually /usr/bin/slirp, to provide IP only networking connectivity through the host. This is similar to IP @@ -1737,7 +1737,7 @@ - 66..1122.. ppccaapp + 6.12. pcap The pcap transport is attached to a UML ethernet device on the command line or with uml_mconsole with the following syntax: @@ -1777,7 +1777,7 @@ - 66..1133.. SSeettttiinngg uupp tthhee hhoosstt yyoouurrsseellff + 6.13. Setting up the host yourself If you don't specify an address for the host side of the ethertap or slip device, UML won't do any setup on the host. So this is what is @@ -1785,7 +1785,7 @@ 192.168.0.251 and a UML-side IP of 192.168.0.250 - adjust to suit your own network): - +o The device needs to be configured with its IP address. Tap devices + o The device needs to be configured with its IP address. Tap devices are also configured with an mtu of 1484. Slip devices are configured with a point-to-point address pointing at the UML ip address. @@ -1805,7 +1805,7 @@ - +o If a tap device is being set up, a route is set to the UML IP. + o If a tap device is being set up, a route is set to the UML IP. UML# route add -host 192.168.0.250 gw 192.168.0.251 @@ -1814,7 +1814,7 @@ - +o To allow other hosts on your network to see the virtual machine, + o To allow other hosts on your network to see the virtual machine, proxy arp is set up for it. @@ -1824,7 +1824,7 @@ - +o Finally, the host is set up to route packets. + o Finally, the host is set up to route packets. host# echo 1 > /proc/sys/net/ipv4/ip_forward @@ -1838,12 +1838,12 @@ - 77.. SShhaarriinngg FFiilleessyysstteemmss bbeettwweeeenn VViirrttuuaall MMaacchhiinneess + 7. Sharing Filesystems between Virtual Machines - 77..11.. AA wwaarrnniinngg + 7.1. A warning Don't attempt to share filesystems simply by booting two UMLs from the same file. That's the same thing as booting two physical machines @@ -1851,7 +1851,7 @@ - 77..22.. UUssiinngg llaayyeerreedd bblloocckk ddeevviicceess + 7.2. Using layered block devices The way to share a filesystem between two virtual machines is to use the copy-on-write (COW) layering capability of the ubd block driver. @@ -1896,7 +1896,7 @@ - 77..33.. NNoottee!! + 7.3. Note! When checking the size of the COW file in order to see the gobs of space that you're saving, make sure you use 'ls -ls' to see the actual @@ -1926,7 +1926,7 @@ - 77..44.. AAnnootthheerr wwaarrnniinngg + 7.4. Another warning Once a filesystem is being used as a readonly backing file for a COW file, do not boot directly from it or modify it in any way. Doing so @@ -1952,7 +1952,7 @@ - 77..55.. uummll__mmoooo :: MMeerrggiinngg aa CCOOWW ffiillee wwiitthh iittss bbaacckkiinngg ffiillee + 7.5. uml_moo : Merging a COW file with its backing file Depending on how you use UML and COW devices, it may be advisable to merge the changes in the COW file into the backing file every once in @@ -2001,7 +2001,7 @@ - 88.. CCrreeaattiinngg ffiilleessyysstteemmss + 8. Creating filesystems You may want to create and mount new UML filesystems, either because @@ -2015,7 +2015,7 @@ should be easy to translate to the filesystem of your choice. - 88..11.. CCrreeaattee tthhee ffiilleessyysstteemm ffiillee + 8.1. Create the filesystem file dd is your friend. All you need to do is tell dd to create an empty file of the appropriate size. I usually make it sparse to save time @@ -2032,7 +2032,7 @@ - 88..22.. AAssssiiggnn tthhee ffiillee ttoo aa UUMMLL ddeevviiccee + 8.2. Assign the file to a UML device Add an argument like the following to the UML command line: @@ -2045,7 +2045,7 @@ - 88..33.. CCrreeaattiinngg aanndd mmoouunnttiinngg tthhee ffiilleessyysstteemm + 8.3. Creating and mounting the filesystem Make sure that the filesystem is available, either by being built into the kernel, or available as a module, then boot up UML and log in. If @@ -2096,7 +2096,7 @@ - 99.. HHoosstt ffiillee aacccceessss + 9. Host file access If you want to access files on the host machine from inside UML, you @@ -2112,7 +2112,7 @@ files contained in it just as you would on the host. - 99..11.. UUssiinngg hhoossttffss + 9.1. Using hostfs To begin with, make sure that hostfs is available inside the virtual machine with @@ -2151,7 +2151,7 @@ - 99..22.. hhoossttffss aass tthhee rroooott ffiilleessyysstteemm + 9.2. hostfs as the root filesystem It's possible to boot from a directory hierarchy on the host using hostfs rather than using the standard filesystem in a file. @@ -2194,20 +2194,20 @@ UML should then boot as it does normally. - 99..33.. BBuuiillddiinngg hhoossttffss + 9.3. Building hostfs If you need to build hostfs because it's not in your kernel, you have two choices: - +o Compiling hostfs into the kernel: + o Compiling hostfs into the kernel: Reconfigure the kernel and set the 'Host filesystem' option under - +o Compiling hostfs as a module: + o Compiling hostfs as a module: Reconfigure the kernel and set the 'Host filesystem' option under @@ -2228,7 +2228,7 @@ - 1100.. TThhee MMaannaaggeemmeenntt CCoonnssoollee + 10. The Management Console @@ -2240,15 +2240,15 @@ There are a number of things you can do with the mconsole interface: - +o get the kernel version + o get the kernel version - +o add and remove devices + o add and remove devices - +o halt or reboot the machine + o halt or reboot the machine - +o Send SysRq commands + o Send SysRq commands - +o Pause and resume the UML + o Pause and resume the UML You need the mconsole client (uml_mconsole) which is present in CVS @@ -2300,28 +2300,28 @@ You'll get a prompt, at which you can run one of these commands: - +o version + o version - +o halt + o halt - +o reboot + o reboot - +o config + o config - +o remove + o remove - +o sysrq + o sysrq - +o help + o help - +o cad + o cad - +o stop + o stop - +o go + o go - 1100..11.. vveerrssiioonn + 10.1. version This takes no arguments. It prints the UML version. @@ -2342,7 +2342,7 @@ - 1100..22.. hhaalltt aanndd rreebboooott + 10.2. halt and reboot These take no arguments. They shut the machine down immediately, with no syncing of disks and no clean shutdown of userspace. So, they are @@ -2357,7 +2357,7 @@ - 1100..33.. ccoonnffiigg + 10.3. config "config" adds a new device to the virtual machine. Currently the ubd and network drivers support this. It takes one argument, which is the @@ -2378,7 +2378,7 @@ - 1100..44.. rreemmoovvee + 10.4. remove "remove" deletes a device from the system. Its argument is just the name of the device to be removed. The device must be idle in whatever @@ -2397,7 +2397,7 @@ - 1100..55.. ssyyssrrqq + 10.5. sysrq This takes one argument, which is a single letter. It calls the generic kernel's SysRq driver, which does whatever is called for by @@ -2407,14 +2407,14 @@ - 1100..66.. hheellpp + 10.6. help "help" returns a string listing the valid commands and what each one does. - 1100..77.. ccaadd + 10.7. cad This invokes the Ctl-Alt-Del action on init. What exactly this ends up doing is up to /etc/inittab. Normally, it reboots the machine. @@ -2432,7 +2432,7 @@ - 1100..88.. ssttoopp + 10.8. stop This puts the UML in a loop reading mconsole requests until a 'go' mconsole command is received. This is very useful for making backups @@ -2448,7 +2448,7 @@ - 1100..99.. ggoo + 10.9. go This resumes a UML after being paused by a 'stop' command. Note that when the UML has resumed, TCP connections may have timed out and if @@ -2462,10 +2462,10 @@ - 1111.. KKeerrnneell ddeebbuuggggiinngg + 11. Kernel debugging - NNoottee:: The interface that makes debugging, as described here, possible + Note: The interface that makes debugging, as described here, possible is present in 2.4.0-test6 kernels and later. @@ -2485,7 +2485,7 @@ - 1111..11.. SSttaarrttiinngg tthhee kkeerrnneell uunnddeerr ggddbb + 11.1. Starting the kernel under gdb You can have the kernel running under the control of gdb from the beginning by putting 'debug' on the command line. You will get an @@ -2498,7 +2498,7 @@ There is a transcript of a debugging session here <debug- session.html> , with breakpoints being set in the scheduler and in an interrupt handler. - 1111..22.. EExxaammiinniinngg sslleeeeppiinngg pprroocceesssseess + 11.2. Examining sleeping processes Not every bug is evident in the currently running process. Sometimes, processes hang in the kernel when they shouldn't because they've @@ -2516,7 +2516,7 @@ Now what you do is this: - +o detach from the current thread + o detach from the current thread (UML gdb) det @@ -2525,7 +2525,7 @@ - +o attach to the thread you are interested in + o attach to the thread you are interested in (UML gdb) att <host pid> @@ -2534,7 +2534,7 @@ - +o look at its stack and anything else of interest + o look at its stack and anything else of interest (UML gdb) bt @@ -2545,7 +2545,7 @@ Note that you can't do anything at this point that requires that a process execute, e.g. calling a function - +o when you're done looking at that process, reattach to the current + o when you're done looking at that process, reattach to the current thread and continue it @@ -2569,12 +2569,12 @@ - 1111..33.. RRuunnnniinngg dddddd oonn UUMMLL + 11.3. Running ddd on UML ddd works on UML, but requires a special kludge. The process goes like this: - +o Start ddd + o Start ddd host% ddd linux @@ -2583,14 +2583,14 @@ - +o With ps, get the pid of the gdb that ddd started. You can ask the + o With ps, get the pid of the gdb that ddd started. You can ask the gdb to tell you, but for some reason that confuses things and causes a hang. - +o run UML with 'debug=parent gdb-pid=<pid>' added to the command line + o run UML with 'debug=parent gdb-pid=<pid>' added to the command line - it will just sit there after you hit return - +o type 'att 1' to the ddd gdb and you will see something like + o type 'att 1' to the ddd gdb and you will see something like 0xa013dc51 in __kill () @@ -2602,12 +2602,12 @@ - +o At this point, type 'c', UML will boot up, and you can use ddd just + o At this point, type 'c', UML will boot up, and you can use ddd just as you do on any other process. - 1111..44.. DDeebbuuggggiinngg mmoodduulleess + 11.4. Debugging modules gdb has support for debugging code which is dynamically loaded into the process. This support is what is needed to debug kernel modules @@ -2823,7 +2823,7 @@ - 1111..55.. AAttttaacchhiinngg ggddbb ttoo tthhee kkeerrnneell + 11.5. Attaching gdb to the kernel If you don't have the kernel running under gdb, you can attach gdb to it later by sending the tracing thread a SIGUSR1. The first line of @@ -2857,7 +2857,7 @@ - 1111..66.. UUssiinngg aalltteerrnnaattee ddeebbuuggggeerrss + 11.6. Using alternate debuggers UML has support for attaching to an already running debugger rather than starting gdb itself. This is present in CVS as of 17 Apr 2001. @@ -2886,7 +2886,7 @@ An example of an alternate debugger is strace. You can strace the actual kernel as follows: - +o Run the following in a shell + o Run the following in a shell host% @@ -2894,10 +2894,10 @@ - +o Run UML with 'debug' and 'gdb-pid=<pid>' with the pid printed out + o Run UML with 'debug' and 'gdb-pid=<pid>' with the pid printed out by the previous command - +o Hit return in the shell, and UML will start running, and strace + o Hit return in the shell, and UML will start running, and strace output will start accumulating in the output file. Note that this is different from running @@ -2917,9 +2917,9 @@ - 1122.. KKeerrnneell ddeebbuuggggiinngg eexxaammpplleess + 12. Kernel debugging examples - 1122..11.. TThhee ccaassee ooff tthhee hhuunngg ffsscckk + 12.1. The case of the hung fsck When booting up the kernel, fsck failed, and dropped me into a shell to fix things up. I ran fsck -y, which hung: @@ -3154,9 +3154,9 @@ The interesting things here are : - +o There are two segfaults on this stack (frames 9 and 14) + o There are two segfaults on this stack (frames 9 and 14) - +o The first faulting address (frame 11) is 0x50000800 + o The first faulting address (frame 11) is 0x50000800 (gdb) p (void *)1342179328 $16 = (void *) 0x50000800 @@ -3399,7 +3399,7 @@ on will be somewhat clearer. - 1122..22.. EEppiissooddee 22:: TThhee ccaassee ooff tthhee hhuunngg ffsscckk + 12.2. Episode 2: The case of the hung fsck After setting a trap in the SEGV handler for accesses to the signal thread's stack, I reran the kernel. @@ -3788,12 +3788,12 @@ - 1133.. WWhhaatt ttoo ddoo wwhheenn UUMMLL ddooeessnn''tt wwoorrkk + 13. What to do when UML doesn't work - 1133..11.. SSttrraannggee ccoommppiillaattiioonn eerrrroorrss wwhheenn yyoouu bbuuiilldd ffrroomm ssoouurrccee + 13.1. Strange compilation errors when you build from source As of test11, it is necessary to have "ARCH=um" in the environment or on the make command line for all steps in building UML, including @@ -3824,8 +3824,8 @@ - 1133..33.. AA vvaarriieettyy ooff ppaanniiccss aanndd hhaannggss wwiitthh //ttmmpp oonn aa rreeiisseerrffss ffiilleessyyss-- - tteemm + 13.3. A variety of panics and hangs with /tmp on a reiserfs filesys- + tem I saw this on reiserfs 3.5.21 and it seems to be fixed in 3.5.27. Panics preceded by @@ -3842,8 +3842,8 @@ - 1133..44.. TThhee ccoommppiillee ffaaiillss wwiitthh eerrrroorrss aabboouutt ccoonnfflliiccttiinngg ttyyppeess ffoorr - ''ooppeenn'',, ''dduupp'',, aanndd ''wwaaiittppiidd'' + 13.4. The compile fails with errors about conflicting types for + 'open', 'dup', and 'waitpid' This happens when you build in /usr/src/linux. The UML build makes the include/asm link point to include/asm-um. /usr/include/asm points @@ -3854,14 +3854,14 @@ - 1133..55.. UUMMLL ddooeessnn''tt wwoorrkk wwhheenn //ttmmpp iiss aann NNFFSS ffiilleessyysstteemm + 13.5. UML doesn't work when /tmp is an NFS filesystem This seems to be a similar situation with the ReiserFS problem above. Some versions of NFS seems not to handle mmap correctly, which UML depends on. The workaround is have /tmp be a non-NFS directory. - 1133..66.. UUMMLL hhaannggss oonn bboooott wwhheenn ccoommppiilleedd wwiitthh ggpprrooff ssuuppppoorrtt + 13.6. UML hangs on boot when compiled with gprof support If you build UML with gprof support and, early in the boot, it does this @@ -3878,7 +3878,7 @@ - 1133..77.. ssyyssllooggdd ddiieess wwiitthh aa SSIIGGTTEERRMM oonn ssttaarrttuupp + 13.7. syslogd dies with a SIGTERM on startup The exact boot error depends on the distribution that you're booting, but Debian produces this: @@ -3897,17 +3897,17 @@ - 1133..88.. TTUUNN//TTAAPP nneettwwoorrkkiinngg ddooeessnn''tt wwoorrkk oonn aa 22..44 hhoosstt + 13.8. TUN/TAP networking doesn't work on a 2.4 host There are a couple of problems which were <http://www.geocrawler.com/lists/3/SourceForge/597/0/> name="pointed out"> by Tim Robinson <timro at trkr dot net> - +o It doesn't work on hosts running 2.4.7 (or thereabouts) or earlier. + o It doesn't work on hosts running 2.4.7 (or thereabouts) or earlier. The fix is to upgrade to something more recent and then read the next item. - +o If you see + o If you see File descriptor in bad state @@ -3921,8 +3921,8 @@ - 1133..99.. YYoouu ccaann nneettwwoorrkk ttoo tthhee hhoosstt bbuutt nnoott ttoo ootthheerr mmaacchhiinneess oonn tthhee - nneett + 13.9. You can network to the host but not to other machines on the + net If you can connect to the host, and the host can connect to UML, but you cannot connect to any other machines, then you may need to enable @@ -3972,7 +3972,7 @@ - 1133..1100.. II hhaavvee nnoo rroooott aanndd II wwaanntt ttoo ssccrreeaamm + 13.10. I have no root and I want to scream Thanks to Birgit Wahlich for telling me about this strange one. It turns out that there's a limit of six environment variables on the @@ -3987,7 +3987,7 @@ - 1133..1111.. UUMMLL bbuuiilldd ccoonnfflliicctt bbeettwweeeenn ppttrraaccee..hh aanndd uuccoonntteexxtt..hh + 13.11. UML build conflict between ptrace.h and ucontext.h On some older systems, /usr/include/asm/ptrace.h and /usr/include/sys/ucontext.h define the same names. So, when they're @@ -4007,7 +4007,7 @@ - 1133..1122.. TThhee UUMMLL BBooggooMMiippss iiss eexxaaccttllyy hhaallff tthhee hhoosstt''ss BBooggooMMiippss + 13.12. The UML BogoMips is exactly half the host's BogoMips On i386 kernels, there are two ways of running the loop that is used to calculate the BogoMips rating, using the TSC if it's there or using @@ -4019,7 +4019,7 @@ - 1133..1133.. WWhheenn yyoouu rruunn UUMMLL,, iitt iimmmmeeddiiaatteellyy sseeggffaauullttss + 13.13. When you run UML, it immediately segfaults If the host is configured with the 2G/2G address space split, that's why. See ``UML on 2G/2G hosts'' for the details on getting UML to @@ -4027,7 +4027,7 @@ - 1133..1144.. xxtteerrmmss aappppeeaarr,, tthheenn iimmmmeeddiiaatteellyy ddiissaappppeeaarr + 13.14. xterms appear, then immediately disappear If you're running an up to date kernel with an old release of uml_utilities, the port-helper program will not work properly, so @@ -4039,7 +4039,7 @@ - 1133..1155.. AAnnyy ootthheerr ppaanniicc,, hhaanngg,, oorr ssttrraannggee bbeehhaavviioorr + 13.15. Any other panic, hang, or strange behavior If you're seeing truly strange behavior, such as hangs or panics that happen in random places, or you try running the debugger to see what's @@ -4059,7 +4059,7 @@ If you want to be super-helpful, read ``Diagnosing Problems'' and follow the instructions contained therein. - 1144.. DDiiaaggnnoossiinngg PPrroobblleemmss + 14. Diagnosing Problems If you get UML to crash, hang, or otherwise misbehave, you should @@ -4078,7 +4078,7 @@ ``Kernel debugging'' UML first. - 1144..11.. CCaassee 11 :: NNoorrmmaall kkeerrnneell ppaanniiccss + 14.1. Case 1 : Normal kernel panics The most common case is for a normal thread to panic. To debug this, you will need to run it under the debugger (add 'debug' to the command @@ -4128,7 +4128,7 @@ to get that information from the faulting ip. - 1144..22.. CCaassee 22 :: TTrraacciinngg tthhrreeaadd ppaanniiccss + 14.2. Case 2 : Tracing thread panics The less common and more painful case is when the tracing thread panics. In this case, the kernel debugger will be useless because it @@ -4161,7 +4161,7 @@ backtrace in and wait for our crack debugging team to fix the problem. - 1144..33.. CCaassee 33 :: TTrraacciinngg tthhrreeaadd ppaanniiccss ccaauusseedd bbyy ootthheerr tthhrreeaaddss + 14.3. Case 3 : Tracing thread panics caused by other threads However, there are cases where the misbehavior of another thread caused the problem. The most common panic of this type is: @@ -4227,7 +4227,7 @@ - 1144..44.. CCaassee 44 :: HHaannggss + 14.4. Case 4 : Hangs Hangs seem to be fairly rare, but they sometimes happen. When a hang happens, we need a backtrace from the offending process. Run the @@ -4257,7 +4257,7 @@ - 1155.. TThhaannkkss + 15. Thanks A number of people have helped this project in various ways, and this @@ -4274,20 +4274,20 @@ bookkeeping lapses and I forget about contributions. - 1155..11.. CCooddee aanndd DDooccuummeennttaattiioonn + 15.1. Code and Documentation Rusty Russell <rusty at linuxcare.com.au> - - +o wrote the HOWTO <http://user-mode- + o wrote the HOWTO <http://user-mode- linux.sourceforge.net/UserModeLinux-HOWTO.html> - +o prodded me into making this project official and putting it on + o prodded me into making this project official and putting it on SourceForge - +o came up with the way cool UML logo <http://user-mode- + o came up with the way cool UML logo <http://user-mode- linux.sourceforge.net/uml-small.png> - +o redid the config process + o redid the config process Peter Moulder <reiter at netspace.net.au> - Fixed my config and build @@ -4296,18 +4296,18 @@ Bill Stearns <wstearns at pobox.com> - - +o HOWTO updates + o HOWTO updates - +o lots of bug reports + o lots of bug reports - +o lots of testing + o lots of testing - +o dedicated a box (uml.ists.dartmouth.edu) to support UML development + o dedicated a box (uml.ists.dartmouth.edu) to support UML development - +o wrote the mkrootfs script, which allows bootable filesystems of + o wrote the mkrootfs script, which allows bootable filesystems of RPM-based distributions to be cranked out - +o cranked out a large number of filesystems with said script + o cranked out a large number of filesystems with said script Jim Leu <jleu at mindspring.com> - Wrote the virtual ethernet driver @@ -4375,176 +4375,176 @@ David Coulson <http://davidcoulson.net> - - +o Set up the usermodelinux.org <http://usermodelinux.org> site, + o Set up the usermodelinux.org <http://usermodelinux.org> site, which is a great way of keeping the UML user community on top of UML goings-on. - +o Site documentation and updates + o Site documentation and updates - +o Nifty little UML management daemon UMLd + o Nifty little UML management daemon UMLd <http://uml.openconsultancy.com/umld/> - +o Lots of testing and bug reports + o Lots of testing and bug reports - 1155..22.. FFlluusshhiinngg oouutt bbuuggss + 15.2. Flushing out bugs - +o Yuri Pudgorodsky + o Yuri Pudgorodsky - +o Gerald Britton + o Gerald Britton - +o Ian Wehrman + o Ian Wehrman - +o Gord Lamb + o Gord Lamb - +o Eugene Koontz + o Eugene Koontz - +o John H. Hartman + o John H. Hartman - +o Anders Karlsson + o Anders Karlsson - +o Daniel Phillips + o Daniel Phillips - +o John Fremlin + o John Fremlin - +o Rainer Burgstaller + o Rainer Burgstaller - +o James Stevenson + o James Stevenson - +o Matt Clay + o Matt Clay - +o Cliff Jefferies + o Cliff Jefferies - +o Geoff Hoff + o Geoff Hoff - +o Lennert Buytenhek + o Lennert Buytenhek - +o Al Viro + o Al Viro - +o Frank Klingenhoefer + o Frank Klingenhoefer - +o Livio Baldini Soares + o Livio Baldini Soares - +o Jon Burgess + o Jon Burgess - +o Petru Paler + o Petru Paler - +o Paul + o Paul - +o Chris Reahard + o Chris Reahard - +o Sverker Nilsson + o Sverker Nilsson - +o Gong Su + o Gong Su - +o johan verrept + o johan verrept - +o Bjorn Eriksson + o Bjorn Eriksson - +o Lorenzo Allegrucci + o Lorenzo Allegrucci - +o Muli Ben-Yehuda + o Muli Ben-Yehuda - +o David Mansfield + o David Mansfield - +o Howard Goff + o Howard Goff - +o Mike Anderson + o Mike Anderson - +o John Byrne + o John Byrne - +o Sapan J. Batia + o Sapan J. Batia - +o Iris Huang + o Iris Huang - +o Jan Hudec + o Jan Hudec - +o Voluspa + o Voluspa - 1155..33.. BBuugglleettss aanndd cclleeaann--uuppss + 15.3. Buglets and clean-ups - +o Dave Zarzycki + o Dave Zarzycki - +o Adam Lazur + o Adam Lazur - +o Boria Feigin + o Boria Feigin - +o Brian J. Murrell + o Brian J. Murrell - +o JS + o JS - +o Roman Zippel + o Roman Zippel - +o Wil Cooley + o Wil Cooley - +o Ayelet Shemesh + o Ayelet Shemesh - +o Will Dyson + o Will Dyson - +o Sverker Nilsson + o Sverker Nilsson - +o dvorak + o dvorak - +o v.naga srinivas + o v.naga srinivas - +o Shlomi Fish + o Shlomi Fish - +o Roger Binns + o Roger Binns - +o johan verrept + o johan verrept - +o MrChuoi + o MrChuoi - +o Peter Cleve + o Peter Cleve - +o Vincent Guffens + o Vincent Guffens - +o Nathan Scott + o Nathan Scott - +o Patrick Caulfield + o Patrick Caulfield - +o jbearce + o jbearce - +o Catalin Marinas + o Catalin Marinas - +o Shane Spencer + o Shane Spencer - +o Zou Min + o Zou Min - +o Ryan Boder + o Ryan Boder - +o Lorenzo Colitti + o Lorenzo Colitti - +o Gwendal Grignou + o Gwendal Grignou - +o Andre' Breiler + o Andre' Breiler - +o Tsutomu Yasuda + o Tsutomu Yasuda - 1155..44.. CCaassee SSttuuddiieess + 15.4. Case Studies - +o Jon Wright + o Jon Wright - +o William McEwan + o William McEwan - +o Michael Richardson + o Michael Richardson - 1155..55.. OOtthheerr ccoonnttrriibbuuttiioonnss + 15.5. Other contributions Bill Carr <Bill.Carr at compaq.com> made the Red Hat mkrootfs script |