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Release Notes for Debian GNU/Linux 4.0 ("etch"), S/390
Chapter 5 - Issues to be aware of for etch

5.1 Potential problems

Sometimes, changes have side-effects we cannot reasonably avoid, or we expose bugs somewhere else. We document here the issues we are aware of. Please also read the errata, the relevant packages' documentation, bug reports and other information mentioned in Further reading, Section 6.1.

5.1.1 Problems with devices related to udev

Although udev has been tested extensively, you may experience minor problems with some devices that will need to be fixed. The most common problems are changed permission and/or ownership of a device. In some cases a device may not be created by default (e.g. /dev/video and /dev/radio).

udev provides configuration mechanisms to deal with these issues. See udev(8) and /etc/udev for further information.

5.1.2 Some applications may no longer work with a 2.4 kernel

Some applications in etch may no longer work with a 2.4 kernel, for example because they require epoll() support, which is not available in 2.4 kernels. Such applications may either not work at all or not work correctly until the system has been rebooted with a 2.6 kernel.

One example is the HTTP proxy squid.

5.1.3 Certain network sites cannot be reached by TCP

Since 2.6.17, Linux aggressively uses TCP window scaling which is specified in RFC 1323. Some servers have a broken behavior, and announce wrong window sizes for themselves. For more details, please see the bug reports #381262, #395066, #401435.

There are usually two workarounds to these problems: either revert the maximum allowed TCP window sizes to a smaller value (preferable) or turn off TCP window scaling altogether (deprecated). See the example commands in the debian-installer errata page.

5.1.4 Slower updates of APT package index files

By default, the etch version of apt uses a new way to update APT package index files (when you run aptitude update) which downloads differences files (instead of the full package index file) called pdiff. This new feature should use less bandwidth and be faster for most systems. Unfortunately, it can also have the opposite effect of making the updates slower on systems with fast network connections (or a very nearby mirror) which are infrequently updated, as it might take more time for the system to merge the differences files than to download a full package index. It is possible to disable this feature by adding Acquire::Pdiffs "false"; to the /etc/apt/apt.conf configuration file.

This change mostly affects users of the unstable and testing branch of Debian GNU/Linux, due to the changing nature of these archives. Users of etch will notice this feature mainly when updating their package status for the security archive.

5.1.5 Asynchronous network initialization may cause unpredictable behavior

On systems which use udev to load drivers for network interfaces, it is possible due to the asynchronous nature of udev that the network driver will not be loaded before /etc/init.d/networking runs on system boot. Although including allow-hotplug to /etc/network/interfaces (in addition to auto) will ensure that the network interface is enabled once it becomes available, there is no guarantee that this will finish before the boot sequence begins to start network services, some of which may not behave correctly in the absence of the network interface.

5.1.6 Problems with non-ASCII characters in filenames

Mounting vfat, ntfs or iso9660 file systems with files that include non-ASCII characters in their filenames will give failures when one tries to use the filenames unless mounting is done with the utf8 option. An indication might be the following failure: 'Invalid or incomplete multibyte or wide character'. A possible solution is to use defaults,utf8 as mount options for vfat, ntfs and iso9660 file systems when they contain filenames with non-ASCII characters.

Note that the Linux kernel does not support case-insensitive filename handling for vfat when the utf8 option is used.

5.1.7 Sound stops working

In rare cases the sound might stop working after the upgrade. If this happens, go through the alsa checklist: run alsaconf as root user, add your user to the audio group, use alsamixer and make sure levels are up and it is unmuted, make sure arts or esound stopped, make sure OSS modules unloaded, make sure speakers are on, check whether the command cat /dev/urandom > /dev/dsp works for root.

5.2 Upgrading to a 2.6 kernel

The 2.6 kernel series contains major changes from the 2.4 series. Modules have been renamed and a lot of drivers have been partially or sometimes almost completely rewritten. Upgrading to a 2.6 kernel from an earlier version is therefore not a process to be undertaken lightly. This section aims to make you aware of some of the issues you may face.

If you compile your own kernel from source, make sure you install module-init-tools before you reboot with the 2.6 kernel. This package replaces modutils for 2.6 kernels. If you install one of the Debian linux-image packages, this package will be installed automatically because of dependencies.

If you use LVM, you should also install lvm2 before you reboot as the 2.6 kernel does not directly support LVM1. To access LVM1 volumes, the compatibility layer of lvm2 (the dm-mod module) is used. You can leave lvm10 installed; the init scripts will detect which kernel is used and execute the appropriate version.

If you have entries in the /etc/modules file (the list of modules to be loaded during system boot), be aware that some module names may have changed. If this happens you will have to update this file with the new module names.

Once you have installed your 2.6 kernel, but before you reboot, make sure you have a recovery method. First, make sure that the bootloader configuration has entries for both the new kernel and the old, working 2.4 kernel. You should also ensure you have a "rescue" floppy or CD-ROM to hand, in case misconfiguration of the bootloader prevents you from booting the old kernel.

5.3 XFree86 to X.Org transition

The transition to X.Org involves some structural changes. In case all installed packages are from Debian and also included in etch, the upgrade should work without problems. However, experience has shown that there are a few changes to be aware of, as they can potentially cause issues during the upgrade.

The most important change is that /usr/X11R6/bin has been dropped and only remains as a symlink to /usr/bin. This means the directory has to be empty at the time the new packages are installed. The new packages conflict with most packages that used /usr/X11R6/bin, but in some cases manual intervention may be needed. Please remember to not run the distribution upgrade from within an X session.

In case the upgrade aborts during X.Org installation, you should check if any files are still left in /usr/X11R6/bin. You can then use dpkg -S to find out which Debian package installed that file (if any), and remove such packages with dpkg --remove. Please make a note which packages you remove, so that you can install substitute packages later on. Before continuing with the upgrade, all files in /usr/X11R6/bin need to be removed.

Please read http://wiki.debian.org/Xorg69To7 for more details and other issues.

If you experience problems with X.Org after restarting, it might be also worth to restart the font server by running /etc/init.d/xfs restart. This happens due to /etc/X11/fs/xfs.options containing a line with no-restart-on-upgrade, but the font paths have changed.

5.4 No support for 8-bit displays in many applications

After the upgrade to the X.Org and the latest libraries, X terminals which can only represent colors 8 bits depth will not work. This is because the Cairo 2D vector graphics library (libcairo2) doesn't have 8-bit pseudocolor support. This library is used by the GNOME and Xfce desktops as well as by many desktop applications compiled with the Gtk2+ toolkit, such as abiword.

Known systems that are affected by this include some Sun machines and X terminals from Tektronix, NCD, IBM and SGI, as well as some other remote X windowing systems. You should configure these terminals to use 16-bit colour, if possible.

More information is available in Freedesktop's bug #4945.

5.5 Upgrading from exim to exim4

One of the packages that has been obsoleted by the etch release is the Mail Transfer Agent (MTA) exim, which has been replaced by the completely new package exim4.

exim (version 3.xx) has been unmaintained upstream for years, and Debian has dropped support for that version as well. If you are still using exim 3.xx, please upgrade your exim installation to exim4 manually. Since exim4 is already part of sarge, you can choose to do the upgrade on your sarge system before the upgrade to etch, or after the etch upgrade at your convenience. Just remember that your old exim package is not going to be upgraded and that it won't get security support after support for sarge has been discontinued.

Note that, depending on your configuration of debconf, you may not be asked any configuration question during installation of exim4. If no questions are asked, the system will default to a 'local delivery' setup. Configuration is possible using the command dpkg-reconfigure exim4-config.

The exim4 packages in Debian are extensively documented. The package's home page is http://wiki.debian.org/PkgExim4 on the Debian Wiki, and the README file can be found at http://pkg-exim4.alioth.debian.org/README/README.Debian.html and inside the packages as well.

The README file has a chapter about Packaging, which explains the different package variations we offer, and it has a chapter about Updating from Exim 3, which will help you in doing the actual transition.

5.6 Upgrading apache2

Apache has been upgraded to the new version 2.2. Although this shouldn't impact the average user, there are some potential issues to be aware of.

http://httpd.apache.org/docs/2.2/upgrading.html contains the upstream changes. Please read this page, and remember that especially:

Debian-specific changes include that the string SSL is no longer defined, as ssl is now supported by the default package.

If you are using the experimental ITK MPM (from the apache2-mpm-itk package), the cgi module will not be correctly enabled by default. To properly enable it, you will need to manually disable mod_cgid and enable mod_cgi:

     # cd /etc/apache2/mods-enabled
     # rm cgid.conf cgid.load
     # ln -s ../mods-available/cgi.load .
     # /etc/init.d/apache2 force-reload

5.7 Upgrading Zope and Plone

Zope and all related products have been updated. Many products were also dropped from the distribution (either because they were obsoleted, or because they are incompatible with the newer Zope, CMF or Plone).

Unfortunately there is no easy and guaranteed way to upgrade a complex zope or plone server. Even though Plone includes a migration tool, experience has shown that automatic migrations can easily fail.

For this reason, users are recommended to set up their system so they can continue to run the sarge installation of Zope/Plone alongside the new etch versions while testing the migration.

The easiest and safest way to achieve this, is to make a copy of your sarge system to another hard disk or partition, and then upgrade only one of the two copies. You can then use chroot to run the sarge version in parallel to the etch version.

It is not possible to have the old and new versions of Zope/Plone installed together on an etch system, partly because the old packages depend on python2.3 which cannot be installed together with python2.4.

5.8 Wildcard expansion (globbing) with GNU tar

Previous versions of GNU tar assumed shell-style globbing when extracting files from or listing an archive. For example:

     tar xf foo.tar '*.c'

would extract all files whose names end in '.c'. This behavior was not documented and was incompatible with traditional tar implementations. Therefore, starting from version 1.15.91, GNU tar no longer uses globbing by default. For example, the above invocation is now interpreted as a request to extract from the archive the file named '*.c'.

See /usr/share/doc/tar/NEWS.gz for further information.

5.9 NIS and Network Manager

The version of ypbind included with nis for etch contains support for Network Manager. This support causes ypbind to disable NIS client functionality when Network Manager reports that the computer is disconnected from the network. Since Network Manager will usually report that the computer is disconnected when it is not in use, NIS users with NIS client systems should ensure that Network Manager support is disabled on those systems.

This can be done by either uninstalling the network-manager package, or editing /etc/default/nis to add -no-dbus to YPBINDARGS.

The use of -no-dbus is the default for new installs of Debian, but was not the default in previous releases.

5.10 Deprecated insecure php configurations

For many years, turning on the register_globals settings in PHP has been known to be insecure and dangerous, and this option has defaulted to off for some time now. This configuration is now finally deprecated on Debian systems as too dangerous. The same applies to flaws in safe_mode and open_basedir, which have also been unmaintained for some time.

Starting with this release, the Debian security team does not provide security support for a number of PHP configurations which are known to be insecure. Most importantly, issues resulting from register_globals being turned on will no longer be addressed.

If you run legacy applications that require register_globals, enable it for the respective paths only, e.g. through the Apache configuration file. More information is available in the README.Debian.security file in the PHP documentation directory (/usr/share/doc/php4, /usr/share/doc/php5).

5.11 Security status of Mozilla products

The Mozilla programs firefox and thunderbird (rebranded in Debian to iceweasel and icedove, respectively), are important tools for many users. Unfortunately the upstream security policy is to urge users to update to new upstream versions, which conflicts with Debian's policy of not shipping large functional changes in security updates. We cannot predict it today, but during the lifetime of etch the Debian Security Team may come to a point where supporting Mozilla products is no longer feasible and announce the end of security support for Mozilla products. You should take this into account when deploying Mozilla and consider alternatives available in Debian if the absence of security support would pose a problem for you.

5.12 KDE desktop

KDE media handling has changed in the version available in etch from using device:/ to media:/. Some user configuration files might have stored device:/ links in them which should be adapted. Notably, ~/.kde/share/apps/konqsidebartng/virtual_folders/services contains this reference and can be safely deleted as it will not be created when setting up new users.

There have been many changes in the KDE desktop environment from the version shipped in sarge to the version in etch, you can find more information in the KDE 3.5 Release Notes.

5.13 GNOME desktop changes and support

If you used the GNOME desktop in sarge you will not benefit from some of the changes introduced in the default configuration in Debian for etch. In some extreme cases the GNOME desktop might not properly handle your old configuration and might not behave properly.

If you have not heavily invested in configuring your GNOME desktop you might want to move the .gconf directory in user's home directories to a different name (such as .gconf.old) so that it gets recreated, with the default configuration for etch, upon starting a new session.

With the release of etch, Debian no longer contains packages for most of the obsolete version 1 release of GNOME, although some packages remain in order to support some Debian packages which have not yet been updated to GNOME 2. Packages for GTK1.2 remain fully maintained.

There have been many changes in the GNOME desktop environment from the version shipped in sarge to the version in etch, you can find more information in the GNOME 2.14 Release Notes.

5.14 Default editor

If you were using vim as your default editor, this may be changed to nano during the upgrade.

Administrators who wish to change the default editor for all users will have to update the alternatives system using:

     # update-alternatives --config editor

Users wishing to change the default editor can define the environment variable EDITOR by introducing the following lines in their own profiles:

     export EDITOR
     alias editor=$EDITOR

5.15 Message of the day

/etc/motd is now a symlink to /var/run/motd which is rebuilt by /etc/init.d/bootmisc.sh from a template, /etc/motd.tail, at each reboot. It means that changes made to /etc/motd will be lost. Changes made into /etc/motd.tail are not automatically applied to /etc/motd other than at reboot.

Also, the EDITMOTD variable at /etc/default/rcS no longer has any effect. If you wish to disable updating of the motd, or want to maintain your own content for the message of the day you just have to point the /etc/motd symlink to a different file such as /etc/motd.static and make your changes there.

5.16 Not default support for unicode in emacs21*

Emacs21 and emacs21-nox are not configured to use Unicode by default. For more information and a workaround please see Bug #419490.

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Release Notes for Debian GNU/Linux 4.0 ("etch"), S/390

$Id: release-notes.en.sgml,v 1.312 2007-08-16 22:24:38 jseidel Exp $

Josip Rodin, Bob Hilliard, Adam Di Carlo, Anne Bezemer, Rob Bradford, Frans Pop (current), Andreas Barth (current), Javier Fernández-Sanguino Peña (current), Steve Langasek (current)