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diff --git a/faq/old_faq.txt b/faq/old_faq.txt new file mode 100644 index 00000000..98c605eb --- /dev/null +++ b/faq/old_faq.txt @@ -0,0 +1,509 @@ +[[!meta copyright="Copyright © 2001, 2002, 2003, 2004, 2005, 2008, 2013 Free +Software Foundation, Inc."]] + +[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable +id="license" text="Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no Invariant +Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] + +[[!tag faq/old]] + + Frequently Asked Questions about the GNU Hurd + +This document attempts to answer the questions that most often plague +users when they are talking about, installing, using, compiling and +developing the GNU Hurd as well as its binary distribution Debian +GNU/Hurd. Be sure to read this before asking for help. + +The GNU Hurd is under active development and a stable version has not +yet been released. Be aware that: there is a lot of work yet to be +completed; you will find bugs; your system will crash. That said, there +is a lot of room for contributions at all levels: development of the +Hurd and Mach proper, porting applications, writing documentation and, +most importantly, user feedback. + +Should you have a question that is not answered by this document and you +feel that it should be, submit it and, if possible, with an answer. + +Each section is copyright its respective author(s). Permission is +granted to copy, distribute and/or modify this document under the terms +of the GNU Free Documentation License, Version 1.1 or any later version +published by the Free Software Foundation; with no Invariant Sections, +with no Front-Cover Texts and with no Back-Cover Texts. A copy of the +license is included in the file COPYRIGHT. + + Neal H Walfield + neal@cs.uml.edu + +? Installation + +?? What partition type should I use for my GNU/Hurd partitions? + +{MB} You should use an ext2 filesystem. Alternatively, you may use BSD +style ufs. The partition type number for ext2fs is 0x83 (this is the +same as in Linux), not 0x63 (GNU HURD). Thomas explains why 0x63 is the +wrong choice: + + One day we may have a new filesystem format, which would + probably be called the GNU Hurd filesystem format, and might + well use that partition code. + +Regardless, as Roland points out, it is always an error to use that code +for an ext2fs partition, + +?? How do I name partitions? + +{MB,NHW} I knew you would ask this. If I had to reduce this FAQ to only +one question, I'd choose this one. It is pretty easy, but you have to +know that there are actually several incompatibly naming convention. + +First, the Hurd: if the disk is question is a SCSI disk, you must know +the SCSI device number; if it is an IDE disk, you must know what +controller the disk is on and whether it is a master or a slave. The +Hurd uses the BSD naming convention which, is to say, disks are ordered +according to their physical location, numerically, starting from zero. +This naming scheme is quite similar to that found in Linux. There, the +master disk on the primary controller is designated as `hda' and the +slave as `hdb'. On the secondary controller, the master and the slave +are designated by `hdc' and `hdd' respectively. Under the Hurd, `hda' +would become `hd0', `hdb' would be referred to as `hd1', etc. + +In the Hurd, like in BSD, partitions are called `slices' and are +numbered starting from one. Thus, to name a particular partition, we +take the disk name, append a `s' and the partition number. Again, this +is similar to Linux except, there is no `s'. For instance, `hda1' would +become `hd0s1'. + +GRUB, the boot loader, uses a completely different nomenclature: it +probes the BIOS and appends each disk in turn to an array. Disks are enumerated +using zero based arrays. GRUB 2 enumerates partitions from one, while GRUB 1 +used to enumerate them from zero. +The format is: +`hd (<disk>, <partition>)'. Thus, in GRUB 2 `hd (0, 1)' refers to the first +partition on the first drive detected by the BIOS (or the second partition with +GRUB 1). As Grub now has tab +completion, there is not a lot of guess work. + +?? How much swap do I need? + +{ST} The usual rule of thumb applies: the same amount as RAM, for instance. + +?? Can I share swap space between GNU/Linux and GNU/Hurd? + +{NHW} Yes. The default pager recognises and respects Linux swap +partitions. It will also swap to a raw partition, i.e. anything that it +does not recognize as Linux swap. Therefore: BE CAREFUL. + +?? Why do I get ``Operation not permitted error''? + +{MB} You forgot to set the file system owner of the GNU/Hurd partition to +``hurd''. The Hurd uses additional information in the inodes to set +translators. To make this work, the partition must be marked as ``owned +by the Hurd''. This is normally done by passing the `-o hurd' option to +`mke2fs' when creating ext2 system from other operating systems +(filesystems created in GNU/Hurd automatically enable this option). +If you failed to do this, you can still use the `e2os' script. + +?? After `native-install' is finished, I had to write tthhiiss + wwaayy. In particular, I had to type `rreebboooott' to reboot. + +{MB} Funny, isn't it? In addition to the rescue `term' server in +`/tmp/console', another `term' server got started and is clobbing the +keyboard input. After a reboot this problem vanishes as only one `term' +server will remain. If `tar' would support translator, we would not +have this problem... Even if you don't experience this problem right +after the installation, reboot immediately so you don't hit this bug by +accident. + +? Setup + +?? How do I add a swap partition? + +{MB} A swap partition is also called a paging file. Usually, it is +sufficient to add the swap partition to `/etc/fstab', just as you would +under Linux. You can swap to a Linux swap partition and the Hurd will +honour the Linux swap signature (both versions). The Hurd will just as +happily swap to any other raw disk space and overwrite anything it +finds. So, be careful! + +If you want to swap to a file or make sure that it checks the Linux swap +signature before, you need to edit `/boot/servers.boot'. The syntax is +the partition device file name plus, optionally, the swap file inside an +ext2fs partition, followed by a space and then one of: +`$(add-raw-paging-file)', `$(add-linux-paging-file)', +`$(add-paging-file)'. The first works with any partition or file and +does not honour any swap signature or other data. The second has a +safety check and only uses the file if a Linux swap signature is found. +The third looks for a swap signature first and falls back to raw paging +if it failed to find one. This is also the default for entries in +`/etc/fstab'. + +?? How do I set up a network? + How do I set up a loopback device? + +{MB} In the former case, be sure that GNU Mach detected your network +card. Either way, you need to setup `pfinet'. Documentation can be +found at: + + http://www.debian.org/ports/hurd/hurd-doc-server#pfinet + +Don't forget to fill in `/etc/resolv.conf', `/etc/hosts', etc. + +Of course, you only need to do this if the installation routine didn't +do it for you. + +?? Can I use the GNU/Linux version of `e2fsck' on a GNU/Hurd partition? + +{MB} Yes, at least since `e2fsprogs-1.05'. Check this with `e2fsck -V' +first. + +{NHW} Do not try to defrag your partition as this utility does not know +about translators. + +?? Why are pipes not working? + +{MB} `settrans -fgc /servers/socket/1 /hurd/pflocal' should help. + +? Usage + +?? Where is the documentation? + +{NHW,MM} There are neither man pages nor info nodes for the Hurd +translators and commands. Documentation lives inside of the binaries +and can be found by passing the `--help' option to a given command. +For instance: + + # /hurd/ext2fs --help + +will tell you what types of options the ext2fs translator accepts. + +The GNU/Hurd User's Guide and the GNU Hurd Reference Manual both +provide some help about the usage of and concepts behind the GNU Hurd. +You can find them, among others, at: + + http://www.gnu.org/software/hurd/docs.html + +?? What is a translator? + +{MB} There is a text about translators available at: + + http://www.debian.org/ports/hurd/hurd-doc-translator + +Read this and ask further questions on the mailing lists. + +?? What is the login shell? + +{MB} The Hurd has the concept of a not-logged in user. This user has +neither user ids nor groups ids. This stems from the fact that the Hurd +supports uid and gid sets and one possibility is, of course, the empty +set. Rather than deny access in this case, filesystems in the Hurd offer a +fourth permission triplet (i.e. rwx) which is used to determine the +privileges for users with no credentials. This, however, needs to be +enabled on a file by file basis. By default, the `other' permission +triplet is used. + +The Hurd login shell is a shell running with neither uids nor gids. To +restrict access to your files, either enable and change the fourth +permission triplet or change the login shell of the `login' user in the +password file to `/bin/loginpr' which implements the standard login +prompt. + +?? How do I use non-US keyboard bindings? + +{ST} On Debian Hurd, you can configure the console layout from +`/etc/default/hurd-console`. + +?? How do I enable color on the console? + +{NHW} If you are using the GNU Mach microkernel, you can set your +terminal to `mach-color'. For instance: + + # export TERM=mach-color + +?? How can I enable virtual consoles? + +{ST} On Debian Hurd, it is already enabled by default, and configured from +`/etc/default/hurd-console`. + +{AMS} This can be done by running the following command: + + console -d vga -d pc_kbd -d generic_speaker /dev/vcs + +If something went wrong, or if you just wish to exit the Hurd console +then hitting C-A-<backspace> will exit it. + +?? What is the status of X? + +{MB} It works! The packages are available at any Debian ftp mirror. +XFree86 4.0.2 is available, as are some of the v3 servers. Instructions +on how to use the packages are in the mailing list archive (link follow +later). + +?? What are these strange pids `0`, `2', `3', `4`, and `5`? + +{MB,ST} Zero is the `proc` processus server (and thus does not really have a pid +:) ) Two is the kernel, three is the root filesystem server, four is the `exec` +server (which handles starting programs), five is the `auth` server (which +handles user authentication). + +?? Why does `ps aux' give me strange output? + +{MB,MM} Try `ps Aux'. Indeed, under GNU/Hurd, `ps aux' doesn't list +all processes: it omits the session and group leaders, and the +processes without parent. + +?? I have a hung process that I want to kill, however, `ps' is now + hanging too. + +{MB} Interrupt it and pass it the `-M' option. + +{NHW} By default, `ps' gathers information from both the proc server and +the processes themselves (via their message port). If a process it +hung, it will not be able respond to its message port and thus, ps will +wait forever. The `-M' option instructs ps to not gather information +that would require use of the message port. + +?? Why are my translators dying? + +{NHW} Try passing the `-ap' flag to settrans. By default, settrans only +sets a passive translator, therefore, no output will show up on your +terminal. Using `-ap', however, sets both the active and the passive +translator which, means that the translator starts immediately and its +stderr is connected to you terminal. + +Additionally, the biggest problem is passing relative paths to passive +translators. You cannot predict what the current working directory of a +translator will be when it is setup as a passive translator. + +?? Why can I `read' a directory? + +{MB} It is important to understand that there is nothing special about a +directory under the Hurd, it is just another file. This fits in with +the translator concept where a translator can appear as a directory but +provide also as a file. + +? Trouble shooting + +?? When the APM support in the BIOS spins down my disk drives, the + Hurd is unable to wake up. What's wrong? + +{MB} APM is not supported in the current version of GNU Mach, sorry. +Please disable APM in your BIOS setup. + +?? What are these messages referring to `default pager', `paging', + and `pager request'? + +{MB} The default pager handles virtual memory allocation. If it can't +allocate a new memory page because you are out of memory, some terrible +things may happen. Whenever you get errors referring to any of these, +you either need more memory (make sure you have swap) or you have found +a memory leak. + +?? What is a gratuitous error? + +{MB} This comes from `strerror(EGRATUITOUS)'. If you check glibc's +documentation, it will say that this error code has no purpose. This, +however, is not quite true. You only get this when something terrible +happens. Thomas explains: + + More precisely `EGRATUITOUS' officially means that some server + has responded in an impossible or protocol-violating fashion. + There are some cases in the Hurd where `EGRATUITOUS' is returned + and probably something else should be chosen instead. + +If you can reproduce this error message, please report it. + +?? What does ``computer bought the farm'' mean ? + +{FH} This message is the text that corresponds to the errno code +`EIEIO'. Roland McGrath explains: + + That message is not output by any particular servers at + particular times; rather it is the perror text for the errno + code EIEIO, which is returned by various RPCs and functions + for a variety of "hopeless" error conditions. + + +?? What does ``/dev/hd0s1: MOUNTED READ-ONLY; MUST USE `fsysopts + --writable''' mean? + +{NHW} In this case, /dev/hd0s1 was not unmounted cleanly. The Hurd +will, on boot up, run ``fsck -p'' on any partitions that it finds in +/etc/fstab, so, you may want to consider adding this partition to that +file. If you are sure that the partition is fine, you can run: + + # fsysopts /home --writable + +to ask the translator sitting on /home to change from read-only to +read/write mode. Note that the command is being sent to the filesystem +and not the store (e.g. /dev/hd0s1). + +?? When GNU/Hurd crashes, GNU Mach automatically reboots. Is + there anyway I can make it pause so I can write down the error? + +{MB} Pass the `-H' option to init (add it to the boot command line), and +`init' will tell Mach to enter the kernel debugger instead to rebooting +it. At the debugger prompt (`db>'), you can type `reboot' any time to +reboot the system. + +? Porting + +?? Is porting easy? + +{NHW} Porting applications to GNU/Hurd is relatively easy assuming the +application is POSIX compliant as GNU/Hurd does its best to be a +conforming operating system. + +The most common error made by programmers is assuming the MAXPATHLEN and +PATH_MAX are defined. On most operating systems this is set to a few +thousand, however, on GNU/Hurd, there is no maximum and thus, this is +not set. The correct thing to do is to submit a patch to the upstream +author that allocates memory dynamically. + +? Compiling + +?? Where can I get the source? + +{AMS} Instructions on how to download the CVS tree from Savanah are +available at https://savannah.gnu.org/cvs/?group=hurd + +{NHW} To get the source to the latest debian package, look on any +debian mirror. + +?? Can I cross compile? + +{ST} To REDO. + +{NHW} Yes. If you are running Debian GNU/Linux on IA32, this is quite +easy as there is a cheap cross compiler available; all that is required +is installing the gcc-i386-gnu and mig-i386-gnu Debian packages. When +running configure, you will have to specify tools directly: + + # MIG=/usr/bin/i386-gnu-mig CC=/usr/bin/i386-gnu-gcc \ + ../src/hurd/configure ... + +If you are running another distribution, you will have to do this the +long way. You can find instructions at the Cross Compiling HOW-TO +available at: + + http://hurddocs.sourceforge.net/howto/cross.html + +Farid Hajji <farid.hajji@ob.kamp.net> also talks about his experiences +at: + + http://lists.debian.org/debian-hurd-0012/msg00062.html + +?? Any general tips? + +{NHW} Yeah, building in the source tree is untested. Try: + + # ../src/hurd/configure ... + +? Development + +?? What is OSKit-Mach? + +{NHW,FH} There are two versions of GNU Mac that are in use: GNU Mach +1.x and GNU Mach 2.x, formerly known as OSKit-Mach. The former uses +the drivers from Linux 2.0.x while the latter uses the University of +Utah's OSKit library for drivers. You can find out more about the +OSKit library at: + + http://www.cs.utah.edu/flux/oskit + +GNU Mach 2.x is usable, but some things are still missing or not +working, like the serial port and scsi drivers. This is why GNU Mach +2.0 hasn't released yet and the two versions coexist. + +?? Where is the documentation? + +{NHW} There were several books written on the Mach kernel. The +information that they contain is still mostly pertinent and should be +considered required reading for potential hackers. They can be found +at: + + http://www.cs.cmu.edu/afs/cs/project/mach/public/www/doc/publications.html + +The documentation for the Hurd is quite inadequate. The starting of a +book, ``The GNU Hurd'' is in the doc directory in the Hurd source. You +can read this using: + + # info hurd + +The authoritative place is, of course, the source code; that does not, +however, mean that we would not welcome more documentation. To get +started, take a look at <hurd>/doc/navigating. + +?? How do I make sure that my code is POSIX compliant? + +{NHW} Unfortunately, you have to buy the POSIX standard from IEEE. The +Single Unix Specification version 2, a superset of POSIX, is available +for free on the Internet. Try: + + http://www.unix-systems.org/online.html + +?? Who do I submit patches to? + +{NHW} If they are against the Hurd, Mach or MiG, send a patch to the +bug-hurd mailing list. + +If they are against other packages, the Debian BTS is a good place. In +this case, be sure to advise the debian-hurd mailing list of the bug. + +?? In what format should patches for the Hurd and GNU Mach be? + +{MB} All patches should be sent in unified context diff format (option +`-u' to GNU diff). It is helpful for us if you also use the `-p' +option which includes information about the function changed by a +patch. Changes that are similar can be grouped together in one file, +but unrelated changes should be sent in seperate files. The patches +can be included in the message or as a MIME attachement. They should +not be compressed and/or archived unless they are very large, and if +they are very large it is probably better to store them on-line at +some place and only sent an URL. + +Write a ChangeLog entry for each change, following the format of the +existing files. Here is an example: + + 2000-12-02 Marcus Brinkmann <marcus@gnu.org> + + * ops.c (op_readlink): Before returning, check if the buffer + pointed to by transp is ours. If not, munmap it. + (op_read): Likewise for bp. + (op_readdir): Don't alloca a buffer here. Instead initialize + BUF and BUFSIZE to 0 and let the server (eh, MiG) do it. + munmap BUF before returning. + +The file name and the name of the function changed should always be +spelled out completely, and not abbreviated or otherwise mangled (like +foo.{c,h}), because that would make searching for all changes to a +file or function impossible. Local variable names are all +capitalized. There are two spaces between sentences. You can use +``C-x 4 a'' in Emacs to add a new ChangeLog entry. If you do that +with the mark being in a function, Emacs will automatically fill in +the file and function name for you. + +Do not send in a patch for the ChangeLog file. Rather include the +ChangeLog entries in the message that contains the patch. Patches for +ChangeLog files often conflict. + +If you have the original source tree in the directory `hurd-orig', and +the modified source tree in the directory `hurd', the following +command will produce a good patch (please make sure there are no extra +files like backups in the modified tree, or leave away the option +`-N'). You will need to collect the ChangeLog entries seperately. + + # diff -x ChangeLog -Nurp hurd-orig hurd + + +Answers were given by (in chronological order): +* {NHW} Neal H Walfield <neal@cs.uml.edu> +* {MB} Marcus Brinkmann <Marcus.Brinkmann@ruhr-uni-bochum.de> +* {AMS} Alfred M. Szmidt <ams@gnu.org> +* {OK} Ognyan Kulev <ogi@fmi.uni-sofia.bg> +* {FH} Frédéric Henry <neryel@reveries.info> +* {MM} Manuel Menal <mmenal@hurdfr.org> +* {ST} Samuel Thibault <samuel.thibault@gnu.org> |