Date: Tue, 21 Oct 2003 13:20:09 -0700 From: Andrew Barnert <barnert@myrealbox.com> To: freebsd-questions@freebsd.org Subject: Linux ABI using existing linux setup? Message-ID: <1066767608.2167.206.camel@verdammt.falcotronic.net>
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Hi there. After years of not using BSD, I've recently installed FreeBSD 5.1, and I have some questions about the linux ABI (plus a few other BSD questions). The short version is: Can I use an existing linux installation instead of linux_base (and if so, what do I need to do to set it up), and can I use a Mandrake setup instead of Redhat or Debian? If you can already answer me, just skip the rest of my email; if you need more information, read on: This box dual-boots between FreeBSD 5.1 and Mandrake Cooker (9.2-ish). The Lilo setup was easy, mounting my ext3 partitions was easy, and after configuring my system and installing the emulation/linux_base port, I can now run most of the software I've installed for Mandrake--including commercial software like SMACX and utilities like fdisk. But there are a few problems. For the most part, they're the same problems you'd get running Mandrake 9.x software on a real Redhat 7.x installation, although there are a few that may be BSD-specific. Either way, I'd like to find a solution. First, is there more information available than the chapter in the Handbook? Next, is it possible to just use my existing linux install in place of the libraries from linux_base? I tried just mounting my linux filesystems on /compat/linux, and almost everything dumps core. That's not surprising, but I wanted to try that before asking. But if I mount my linux system in /mnt/linux, executables can't find any of the solibs. I tried running things under a chroot jail, but then everything coredumps. Is the dynamic rerooting thing configurable? Is there anything tricky I need to do here? And if I do need to chroot nearly everything under /mnt/linux, does that mean only root can run linux apps, or can I allow other people to chroot successfully (and how)? Do I need to brandelf all of my linux executables? (And will this affect using them under linux?) Do I need to run an extra ldconfig, passing /mnt/linux/lib, etc.? And do I use /sbin/ldconfig, /compat/linux/sbin/ldconfig, or /mnt/linux/sbin/ldconfig? (Since I don't know the inner workings of the BSD loader as I do linux, I don't want to mess things up and have to reinstall... I was a bit surprised to see that ldconfig runs so quickly, and the only file it seems to keep around, /var/run/ld-elf.so.hints, is only 239 bytes rather than the 100K+ for /etc/ld.so.cache under linux.) Once I get shared library support working, is there any reason I can't use Mandrake's RPM (a modified 4.2) and urpmi and related tools to update my Mandrake installation from within BSD (by repointing the config files and/or chrooting them)? It may be a larger problem with the dynamic rerooting than just so loading. For example, /usr/local/bin/rpm -qa fails because /var/lib/rpm is empty. But /compat/linux/bin/rpm -qa also fails for the same reason, even though /compat/linux/var/lib/rpm is not empty. Meanwhile, in a separate issue, Linux SDL games have no sound. When I run smacx (with sound enabled), after about 10 seconds it prints "SDL: Audio timeout - buggy audio driver? (disabled)" to stderr. If I don't disable sound, I get a long delay every time it tries to play a movie. Otherwise the game works fine, but no sound. The same thing happens with /mnt/linux/usr/bin/playsound (from the SDL audio package), but /usr/local/bin/playsound works fine. (This is all true whether I'm running esd or not--and esddsp doesn't help. Even after I've set sysctl hw.snd.pcm0.vchans=4, nothing changes.) Do I just need to symlink something to [/compat/linux?]/dev/pcm, etc.? If the system crashes without unmounting cleanly (playing with svgalib stuff...), I can run fsck.ext2 under BSD until the penguins come home, and it finds and even fixes problems just fine, but it never marks the filesystems as clean. So, until I reboot into linux once, I can only mount my ext2 filesystems readonly. Is there something I'm missing? Should I run /mnt/linux/sbin/fsck, or is this a dangerously stupid idea? Or is this by design? And speaking of crashes, I assume there's nothing like linux's "magic SysRq hack" in FreeBSD? (Being able to SysRq-SUB to unmount cleanly even after the system is totally hosed is quite nice for kernel/driver/svga/X/etc. hacking.) Finally, I can lilo -R (to change the default boot target (so I can "lilo -r /mnt/linux -R FreeBSD-5.1 && reboot" or "lilo -r /mnt/linux -R linux24229mm && reboot" and walk away), but lilo -q (to see the list of targets, and verify that they can be found) doesn't work. And, needless to say, installing a new boot map doesn't work. I've spoken to the main lilo developer, and looked at the code, and this is pretty much unfixable (unless you want to add a bunch of new IOCTL's into the various fs drivers, or rewrite lilo to do things a different way), but I thought it was worth mentioning. (I can just strings /mnt/linux/boot/map to get all I really need....) Anyway, any help anyone can offer would be greatly appreciated.
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