You have been subscribed to a public bug: ======================================= === Reported by Peter Oberparleiter === =======================================
---Problem Description--- Ubuntu installations performed in IBM Z LPAR via an HMC drive block for a prolonged time (multiple days), making this installation path unusable. The problem exists from Ubuntu 20.04 up to 24.10beta. Machine Type = s390/IBM Z ---boot type--- CDROM / ISO image ---Install repository type--- CDROM ---Point of failure--- The IBM Z Hardware Management Console (HMC) can provide non-networked, in-band access to Linux installation media via its HMC drive function. This function can be used to install Linux in environments where a local FTP server for use as boot and initial installation source is unavailable. Unfortunately access to this function is very slow, with response times up to seconds for reading directories and transferring chunks of installer data. Starting with Ubuntu 19.10, the casper installer component automatically makes use of the HMC drive if it contains a valid Ubuntu installation media [1]. Since Ubuntu 20.04, the Ubuntu installer mounts file-system images contained on the media, and accesses files from those images in place. The resulting random-access pattern to media data in combination with HMC drive response times add up to the observed prolonged wait times. Some ideas how to resolve this problem: 1. Remove HMC drive support from casper. This is not preferred since it would also remove the ability of users to install Ubuntu in environments without FTP server. 2. Make HMC drive support in casper configurable. This could be done e.g. by evaluating a new parameter passed to casper via the kernel command line. To enable users to install with either option without having to change ISO contents, multiple installer .ins files would also need to be added to the installer media. 3. Make use of hcwdrv/hwcdrvfs caching options hmcdrv module parameter 'cachesize=4194304' should be used to maximize transfer chunk size. Also hmcdrvfs should be called with options '-o kernel_cache -o entry_timeout=3600 -o attr_timeout=3600' to ensure that directory and file data is cached longer. 4. Change casper to automatically copy all HMC drive contents to RAM- disk and work with the RAM-disk copy instead. Given the time it takes for a full copy, such a function would need to provide regular ETA on the console to prevent users from aborting the installation due to lack of feedback. [1] https://git.launchpad.net/ubuntu/+source/casper/commit/scripts/casper?id=810c74e4f2894 ** Affects: linux (Ubuntu) Importance: Undecided Assignee: Skipper Bug Screeners (skipper-screen-team) Status: New ** Tags: architecture-s3903164 bugnameltc-210018 severity-high targetmilestone-inin--- -- [UBUNTU 24.04] Installer stalls when using HMC drive https://bugs.launchpad.net/bugs/2083843 You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp
