patch-2.1.43 linux/Documentation/transname.txt
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- Lines: 265
- Date:
Thu Jun 12 16:22:04 1997
- Orig file:
v2.1.42/linux/Documentation/transname.txt
- Orig date:
Wed Dec 31 16:00:00 1969
diff -u --recursive --new-file v2.1.42/linux/Documentation/transname.txt linux/Documentation/transname.txt
@@ -0,0 +1,264 @@
+Transname version 1.9 (C) 1997 Thomas Schoebel-Theuer
+
+transname enables diskless clients, X-terminals etc to mount the
+*root filesystem* of the server. This make administration of
+large pools a lot easier.
+
+Wherefore is linux-2.0.21-transname.patch?
+
+Currently different diskless clients must have their root / on different
+directories on the server, beause each client has _some_ different
+configuration files. However, most files (typically about 99%) have the same
+contents on the clients and on the server, but have to be replicated
+(and maintained separately) just because of the 1% differences.
+This duplication causes very large efforts in practise, since at least
+the /etc directory has to be duplicated for every client. Even in /etc
+many files are identical, for example sendmail.cf, initrc scripts and
+others. Maintaining a large pool means to ensure coherence amoung the
+duplicates. Classical methods like symlinks are unconvenient
+for this task because they have to be valid in the view of mounted
+filesystems at all clients, not at the server.
+
+Linux transname overcomes this problem by allowing filenames
+to be context-dependend. For example, if you have a file /etc/config
+that should differ on the hosts "myserver" and "myclient", you just
+create two different files named /etc/config#host=myserver# and
+/etc/config#host=myclient# . On host "myserver", the file
+/etc/config#host=myserver# will appear as if it were hardlinked to
+file /etc/config (without the #...=...# suffix). On host "myclient",
+the corresponding other file will appear as /etc/config. So you
+can access the right file contents under the _same_ name, depending
+on which host you are working.
+
+A similar concept can be found in elder HP-UX versions, but with
+so-called "hidden directories" which don't allow contemporary viewing
+all versions by default. In contrast, transname shows all context-dependent
+files in the dir listing and they can be edited using the
+fully qualified name.
+
+Transname was developped for and is used at our Linux pool at the
+University of Stuttgart with good results. Maintainance of the pool is
+at a minimum, and adding new clients is a child's play. No worry with
+keeping up mail configurations, newly installed tools, changed /etc/services,
+/etc/shells, /etc/resolv.conf and many, many others. In contrast to a
+sophisticated symlink solution, adding a new file to the /etc directory
+is seen immediately by all clients.
+
+An example for the use of linux-2.0-transname.patch:
+
+For example, you can make your /etc/fstab context-dependend. If you want
+to do that, you should create an /etc/fstab#ktype=default# for the
+server and an /etc/fstab#ktype=diskless# for all clients. This is because
+your clients may not yet know their own hostname when they attempt to mount
+the root filesystem. You can compile in the kerneltypes "default" and
+"diskless" into different kernels for servers and clients. Of course,
+if your clients boot via bootp and know their names when mounting the root,
+you can use /etc/fstab#host=myclient# instead. But at least servers
+booting from disk normally dont know their hostname at root mount time,
+so you can mix methods and use /etc/fstab#ktype=default# for the server,
+/etc/fstab#ktype=diskless# for the majority of the clients and
+/etc/fstab#host=myclient# for some specific client, because translation
+of #host=...# is given precedence over #ktype=...# by default.
+
+This sort of name translation works with any underlying file system
+and with any inode type (i.e. with directories, symlinks, devices etc),
+because it is implemented in the VFS layer of the kernel. Currently,
+five types of default translations are supported:
+
+ * <name>#host=<hostname># depends on the hostname, see "uname -n"
+ * <name>#kname=<string># works with a hard compiled-in string
+ * <name>#ktype=<string># works with a hard compiled-in string
+ * <name>#machine=<id># depends on architecture, see "uname -m"
+ * <name>#system=<id># currently only supported by Linux, see "uname -s"
+
+Others may be added in future.
+
+The current translation are displayed at boot time in the kernel messages
+for easier debugging, and can be retrieved by reading
+/proc/sys/kernel/nametrans which is a special file containing the currently
+valid translations.
+
+The default translations change whenever the hostname(1) is set or changed.
+Thus, the hostname is not set (or set to the name "(none)") at boot time
+before init(8) sets it. So, if you want to use the hostname before that
+moment, there are three ways:
+
+ a) set the hostname before via bootp or similar.
+ b) use the compiled-in translations kname and ktype solely.
+ c) set all translations by lilo (or on the boot command line) with
+ kernel parameter nametrans=#host=banana#:#ktype=diskless# ,
+ thus overriding and hiding the default (built-in) translations.
+
+Note that by supplying the colon-separated list of at most 16 suffixes, you
+can also use other translation types that are not defined in the default
+translations. However, you must ensure that the syntax #...=...# is correct.
+The specified contexts will be tried in the specified order *instead* of the
+default translations.
+
+You can override the default (or parameter-supplied) translations at runtime
+by executing
+echo "#host=$HOST#:#ktype=diskless#:#myconfig=something#" > /proc/sys/kernel/nametrans
+However, after doing this (or setting as kernel parameter) the built-in
+default translations have no effect any more, thus changing the hostname
+will not be reflected in the overridden translations. You can switch
+back to the default translations by executing
+echo "" > /proc/sys/kernel/nametrans
+
+Another drawback is that administration tools currently are not aware of
+context-dependend files, so you cannot switch between contexts inside
+one tool session. However, you can simulate administration sessions
+on the server as if they were running on some client. To do this,
+you have to set an environment variable NAMETRANS which has to be the
+*first* environment variable in the list. For example, you can execute
+'env - NAMETRANS=#host=mango#:#ktype=diskless# "`env`" command ...'
+where the command will see the same files as if it had been executed on host
+"mango" with a "diskless" kernel. To switch off translations entirely, use
+an empty list, e.g. 'env - NAMETRANS= "`env`" command ...'.
+
+Hopefully the creators of administration tools and maintainers of Linux
+distributions will support changing environments in future, so that
+maintaining different views will be very easy.
+
+Some hints:
+
+Archivers like tar, dump, restore should be used with translation
+switched off, in order to avoid doubled space in archive files and when
+extracting from them. Also, make sure that nfsd, mountd (and similar ones
+like samba daemons) run without translation, in order to avoid doubled
+(or even wrong) translation at the server and at the client. You can
+automatically force the creation of context-dependent filenames if there
+exists a template filename like /etc/mtab#host=CREATE#. As soon as a
+process running on "mango" tries to create a file /etc/mtab, the version
+/etc/mtab#host=mango# is created instead (which appears in turn as
+hardlinked to /etc/mtab). Note that if you want to make /etc/fstab
+context-dependend, you should execute "touch /etc/mtab#host=CREATE#" and
+"touch /etc/mtab.tmp#host=CREATE#", because mount, umount and others
+running on different hosts would otherwise try to create one shared
+/etc/mtab which would result in a clash. Also one should execute
+"touch /etc/nologin#host=CREATE#" to prevent global side effects from
+shutdown resp. runlevel.
+
+Which files you have to make context-dependent will differ for different
+needs and different applications. Hopefully some day a standard will
+cover the most common cases and the mist common Linux distributions.
+A HOWTO on this subject is in preparation.
+
+How to install linux-2.0.21-transname.patch?
+
+First of all, keep a backup of your kernel on your disk. Second, keep a
+floppy with a miniroot handy, so you can boot from the floppy, mount
+your harddisk root filesystem and change the names of your configuration
+files back to their old names in case of emergency.
+
+Then, make a kernel with transname support enabled. With "make config"
+or "make xconfig", just go to the section "filesystems". Take a look at
+the help texts that are associated with the transname options, they tell
+you further hints not mentioned in this README. Then build your kernel as
+usual, install it with a *new* kernel-filename, add a *new* entry to
+/etc/lilo.conf and run lilo. **DONT CHANGE** any configuration files for the
+first reboot!
+
+Just reboot the new kernel and play a little bit around with
+creating context-dependend filenames in your home directory.
+Try all modes including setting NAMETRANS to different values.
+
+As an example for the changes necessary on our LST-1.8-based Linux pool,
+here is the output of the command
+find / /tmp -xdev -name "*#*#" -print | sort -u | xargs ls -ld
+
+-r--r--r-- 1 root root 1725 Dec 21 1995 /etc/X11R6/xdm/xdm-config#host=eiche#
+-r--r--r-- 3 root root 9509 Feb 15 17:35 /etc/XF86Config#host=balsa#
+-r--r--r-- 1 root root 9401 Feb 15 17:34 /etc/XF86Config#host=eiche#
+-rw-r--r-- 1 root root 9820 Feb 21 17:00 /etc/XF86Config#host=fichte#
+-rw-r--r-- 1 root root 9822 Feb 14 15:45 /etc/XF86Config#host=laerche#
+-r--r--r-- 3 root root 9509 Feb 15 17:35 /etc/XF86Config#host=mahagoni#
+-r--r--r-- 3 root root 9509 Feb 15 17:35 /etc/XF86Config#host=palisander#
+-r--r--r-- 2 root root 9509 Feb 15 17:41 /etc/XF86Config#host=pcbs10#
+-r--r--r-- 2 root root 9509 Feb 15 17:41 /etc/XF86Config#host=pcbs11#
+-rw-r--r-- 1 root root 586 Jun 11 23:13 /etc/fstab#ktype=default#
+-rw-r--r-- 1 root root 242 May 29 17:35 /etc/fstab#ktype=diskless#
+-rw------- 1 root root 338 Jun 14 16:37 /etc/lilo.conf#host=eiche#
+-rw------- 1 root root 5236 Dec 16 1995 /etc/lst.cnf#host=balsa#
+-rw------- 1 root root 5254 Dec 16 1995 /etc/lst.cnf#host=eiche#
+-rw------- 1 root root 5236 Dec 19 1995 /etc/lst.cnf#host=fichte#
+-rw------- 1 root root 5236 Jan 11 13:47 /etc/lst.cnf#host=laerche#
+-rw------- 1 root root 5236 Feb 14 16:57 /etc/lst.cnf#host=mahagoni#
+-rw------- 1 root root 5236 Jan 4 1996 /etc/lst.cnf#host=palisander#
+-rw------- 1 root root 5236 Feb 15 13:57 /etc/lst.cnf#host=pcbs10#
+-rw------- 1 root root 5236 Feb 14 17:06 /etc/lst.cnf#host=pcbs11#
+-rw-r--r-- 1 root root 0 Dec 18 1995 /etc/mtab#host=CREATE#
+-rw-r--r-- 1 root root 157 Jun 23 21:16 /etc/mtab#host=balsa#
+-rw-r--r-- 1 root root 466 Jul 1 16:15 /etc/mtab#host=eiche#
+-rw-r--r-- 1 root root 239 Jul 4 11:10 /etc/mtab#host=fichte#
+-rw-r--r-- 1 root root 239 Jun 18 14:17 /etc/mtab#host=laerche#
+-rw-r--r-- 1 root root 239 May 23 10:50 /etc/mtab#host=mahagoni#
+-rw-r--r-- 1 root root 239 Jul 3 10:36 /etc/mtab#host=palisander#
+-rw-r--r-- 1 root root 47 Feb 15 14:57 /etc/mtab#host=pcbs10#
+-rw-r--r-- 1 root root 47 Feb 14 20:04 /etc/mtab#host=pcbs11#
+-rw-r--r-- 1 root root 0 Dec 18 1995 /etc/mtab.tmp#host=CREATE#
+-rw-r--r-- 1 root root 0 Dec 19 1995 /etc/nologin#host=CREATE#
+---------- 1 root root 115 Feb 15 14:57 /etc/nologin#host=pcbs10#
+---------- 1 root root 115 Feb 14 20:04 /etc/nologin#host=pcbs11#
+-rw-r--r-- 1 root root 4818 Dec 16 1995 /etc/system.cnf#host=balsa#
+lrwxrwxrwx 1 root root 25 Dec 22 1995 /etc/system.cnf#host=eiche# -> system.cnf#ktype=default#
+-rw-r--r-- 1 root root 4821 Dec 19 1995 /etc/system.cnf#host=fichte#
+-rw-r--r-- 1 root root 4824 Jan 11 13:47 /etc/system.cnf#host=laerche#
+-rw-r--r-- 1 root root 4827 Feb 14 16:57 /etc/system.cnf#host=mahagoni#
+-rw-r--r-- 1 root root 4833 Jan 4 1996 /etc/system.cnf#host=palisander#
+-rw-r--r-- 1 root root 4840 Feb 15 14:10 /etc/system.cnf#host=pcbs10#
+-rw-r--r-- 1 root root 4846 Feb 14 18:23 /etc/system.cnf#host=pcbs11#
+-rw-r--r-- 1 root root 4818 Dec 13 1995 /etc/system.cnf#ktype=default#
+drwxrwxrwt 16 root root 3072 Jul 4 14:29 /tmp#ktype=default#
+lrwxrwxrwx 1 root root 26 Jul 4 14:22 /tmp#ktype=diskless# -> /tmp#ktype=default#/client
+-rw-rw-rw- 1 root root 0 Feb 15 14:57 /tmp/client#host=CREATE#
+drwxrwxrwx 4 root root 1024 Jun 28 12:15 /tmp/client#host=balsa#
+drwxrwxrwx 3 root root 1024 Jul 4 11:10 /tmp/client#host=fichte#
+drwxrwxrwx 3 root root 1024 Jun 18 14:18 /tmp/client#host=laerche#
+drwxrwxrwx 3 root root 1024 May 24 13:06 /tmp/client#host=mahagoni#
+drwxrwxrwx 3 root root 1024 Jul 3 10:37 /tmp/client#host=palisander#
+drwxrwxrwx 4 root root 1024 Feb 15 14:57 /tmp/client#host=pcbs10#
+drwxrwxrwx 3 root root 1024 Feb 20 06:43 /tmp/client#host=pcbs11#
+lrwxrwxrwx 1 root root 9 Feb 15 13:58 /usr/X11R6/bin/X#host=pcbs10# -> XF86_SVGA
+lrwxrwxrwx 1 root root 9 Feb 14 17:37 /usr/X11R6/bin/X#host=pcbs11# -> XF86_SVGA
+lrwxrwxrwx 1 root root 7 Feb 14 17:15 /usr/X11R6/bin/X#ktype=diskless# -> XF86_S3
+drwxr-xr-x 22 root root 1024 Dec 13 1995 /var#host=balsa#
+drwxr-xr-x 23 root root 1024 Jan 12 14:22 /var#host=eiche#
+drwxr-xr-x 22 root root 1024 Dec 13 1995 /var#host=fichte#
+drwxr-xr-x 22 root root 1024 Dec 13 1995 /var#host=laerche#
+drwxr-xr-x 22 root root 1024 Dec 13 1995 /var#host=mahagoni#
+drwxr-xr-x 22 root root 1024 Dec 13 1995 /var#host=palisander#
+drwxr-xr-x 22 root root 1024 Dec 13 1995 /var#host=pcbs10#
+drwxr-xr-x 22 root root 1024 Dec 13 1995 /var#host=pcbs11#
+
+Notes: The /tmp directory has an own filesystem on server "eiche",
+in order to prevent users from filling the whole filestore (we dont use
+quotas). Each client needs a different /tmp because of possible name clashes.
+Also, the whole /var hierarchy is kept differently to prevent any risk, but
+that could be optimized perhaps. Note that nfsd and mountd have been
+replaced by a script which switches off translations, in the style
+
+-rwxr-xr-x 2 root root 70 Mar 22 12:54 /usr/sbin/rpc.mountd
+-rwxr-xr-x 1 root root 32772 Jun 11 1995 /usr/sbin/rpc.mountd.notrans
+-rwxr-xr-x 2 root root 70 Mar 22 12:54 /usr/sbin/rpc.nfsd
+-rwxr-xr-x 1 root root 45060 Jun 11 1995 /usr/sbin/rpc.nfsd.notrans
+
+where /usr/sbin/rpc.mountd has the contents
+
+#!/bin/sh
+exec /usr/bin/env - NAMETRANS= "`/usr/bin/env`" $0.notrans $*
+
+Of course, that could be improved, but is a quick hack to get things work.
+
+Enjoy,
+
+-- Thomas
+
+
+The author can be contacted under
+ schoebel@informatik.uni-stuttgart.de
+or snailmail
+ Thomas Schoebel-Theuer
+ Institut fuer Informatik
+ Breitwiesenstr. 20-22
+ D-70565 Stuttgart
+
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