Tuesday, August 14, 2012

Debian s390x installation now working

With a current daily build of debian-installer you should now be able to install a VM with Debian s390x. I'm told that even installation within hercules works again. d-i's beta 1 for wheezy has a broken busybox and is hence unusable. But there were more issues:
  • zipl-installer was blacklisted from building on s390x by Packages-arch-specific which caused nobootloader to be selected during installation.
  • base-installer was unable to pick the correct kernel image due to it not having any rules for this architecture.
  • A netcfg fix was needed that removes a 50s timeout while d-i tries to arping the configured gateway. This check seems to be pretty new and if it fails the link is still considered up and the installation continues. The network driver commonly used on s390(x) (qeth) uses layer 3 configuration by default, which means that ARP is meaningless. The IPv4 and IPv6 addresses are configured in the network adapter which then does all the ARP if necessary (i.e. not within the same machine).
The resulting installation even boots. But it shares some problems with squeeze's s390 port:
  • udev's persistent network device naming is broken. It includes a volatile device ID that is incremented with each reboot. This is now tracked in Debian bug #684766.
  • The TERM variable is set to linux during boot-up instead of dumb (the s390(x) terminals are either line- or form-based, except for one HMC ASCII terminal). Together with the new fancy coloured LSB init output in wheezy the screen gets even more noisy with all those escape sequences. It's yet unclear where this should be fixed. The kernel provides the init system with a TERM=linux default and it's not yet fixed up afterwards (either in initramfs-tools, or busybox, or sysvinit).
Tip of the day: If you see funny characters in x3270, then you maybe selected the wrong EBCDIC code page. If you use Linux you want to select CP1047 instead of the default CP037 in Options → Character Set (→ Euro). That's the target of the in-kernel ASCII to EBCDIC converter.

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