From Bugzilla Helper: User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.1) Gecko/20021003 Description of problem: Strange behavior running kernel-uml including 1). Hangs (or exceedingly slow startup) at random points in the startup process when services are started 2). UML do not come down cleanly. Processes on the host are left running. 3). Problems when mounting images Version-Release number of selected component (if applicable): How reproducible: Always Steps to Reproduce: I have tried three difference procedures A1. Download root_fs.rh-7.2-full.pristine.20020312.bz2 from http://user-mode-linux.sourceforge.net/dl-sf.html A2. Uncompress image A3. Loop-mount the image A4. Edit /etc/inittab to default to run-level 3 and alter all 'ttys/#' to 'tty#'. A5. Save and umount A6. Execute '/boot/vmlinuz-2.4.18-14uml \ ubd0=root_fs.rh-7.2-full.pristine.20020312 con=xterm' B1. Download root_fs_toms1.7.205.bz2 from the same site as above B2. Uncompress image B3. Loop-mount the image B4. Edit /etc/inittab to default to run-level 3 and alter all 'ttys/#' to 'tty#'. B5. Save and umount B6. Execute '/boot/vmlinuz-2.4.18-14uml \ ubd0=root_fs_toms1.7.205 con=xterm C1. Follow the procedure described at http://linuxhacker.ru/uml/ I did try various settings for RAM, but to no avail. (The RH 7.2 image are slightly altered from the version RH distributes. The ttys/# -> tty# undoes one of these changes. If this is not done no terminals will start and you'll be unable to log in) Actual Results: A: Hangs: The hangs are coming at rather random points in the service startup process (the earliest one is if the disk is to be fsck'd). CTRL+C in the X console seems to break the halt sometimes, but it can hang again later on. I have tried to leave the process hanging to see if it would resume processing and sometimes it did (after waiting several minutes). I havn't seen any hangs in the kernel startup proper. The tomsrtbt image do not hang at all. OTOH: It hardly starts any services... A+B: UML do not come down cleanly. When one shuts the UML kernel down the processes on the host are left running. The problem is the same whatever method you use: uml_mcontrol, 'shutdown -h' from inside the UML kernel or a hard CTRL+C in the host console. Killing the tracing thread sometimes takes all other process down with it, but sometimes not. C: Problems when mounting images (not that important - I tried it out of frustration with the other images) The boot process stops when the installer tries to mount the /base/stage2.img image as root. The problem lies in a script called 'rootmnt' or 'mntroot' or something like that. The actual NFS mount of the installation disks works fine. Expected Results: No hanging processes in the startup and no hanging processes when the UML quits. Additional info: Hardware: Intel Pentium III VIA chipset (VT82C693A/694x, VT82C598/694x, VT82C686) Software: Linux version 2.4.18-17.8.0 (bhcompile.redhat.com) (gcc version 3.2 20020903 (Red Hat Linux 8.0 3.2-7)) #1 Tue Oct 8 13:51:08 EDT 2002 kernel-2.4.18-17.8.0 kernel-uml-2.4.18-14 Note: In addition to this report I am filing an enhancement request for an UML image to be included in the distribution for testing purposes. I don't like filing a bug-report involving modified third party root images, but without an included image there is no other option.
Some additional information: > 2). UML do not come down cleanly. Processes on the host are left > running. ...and consuming huge amounts of CPU power. Here is a listing of the left-over processes after a 'shutdown -h now' command was issued from within the UML: 20924 pts/7 S 0:37 /boot/vmlinuz-2.4.18-14uml [(tracing thread)] 20927 pts/7 S 0:05 /boot/vmlinuz-2.4.18-14uml [(kernel thread)] 20934 pts/7 S 0:00 /boot/vmlinuz-2.4.18-14uml [(kernel thread)] 20936 pts/7 S 0:00 /boot/vmlinuz-2.4.18-14uml [(kernel thread)] 20938 pts/7 S 0:00 /boot/vmlinuz-2.4.18-14uml [(kernel thread)] 20940 pts/7 S 0:00 /boot/vmlinuz-2.4.18-14uml [(kernel thread)] 20942 pts/7 S 0:00 /boot/vmlinuz-2.4.18-14uml [(kernel thread)] 20944 pts/7 S 0:00 /boot/vmlinuz-2.4.18-14uml [(kernel thread)] 20949 pts/7 S 0:00 /boot/vmlinuz-2.4.18-14uml [(kernel thread)] 20952 pts/7 S 0:04 /boot/vmlinuz-2.4.18-14uml [init] 27575 pts/7 S 0:00 /boot/vmlinuz-2.4.18-14uml [/bin/bash] 27663 pts/7 R 69:02 /boot/vmlinuz-2.4.18-14uml [halt] 'top' showed PID 27663 gobling up all available CPU. (As a tribute to the responsiveness of the kernel in RH8, I must mention that I didn't notice any slowdown on the host machine at all, and only discovered the offending process when I did a 'top' much later when working on an unrelated problem :-)
UML is very experimental, its value in the RH shipped is basically as a debugging tool. Linux 2.5 kernel trees have a much better UML environment that may make production grade