[SOLVED] virtualization/chroot of other OSs/GNU/Linuxes

dchmelik · 06-01-2023, 05:31 AM

Lately I setup several other GNU/Linux partitions and chroot into them from Slackware, just to know about those, as I administer some others for users (on other PCs) and in future might work as a computer programmer and/or system administrator and use some others. I also have NetBSD & FreeBSD & DragonFlyBSD UNIXes on partitions and setup reading (not writing, unstable) those (except doesn't work with DragonFlyBSD FFS/UFS) so I don't always have to reboot if I want to save files from one. If something goes wrong with Slackware and I can't fix it right away, sometimes I boot FreeBSD (same /home on ZFS). SlackBuilds.org (SBo) has a SlackBuild for debootstrap which people use to install Debian in a chroot. I used to use Debian in late 1990s and early '0s so would rather try Devuan... their installer didn't work for me, eventually always showing disorganized mess of lines on an AMD Radeon RX 6900 XT regardless of monitor (I think everything newer than FreeBSD has problems with the exception of OpenBSD).
        Ones I tried so far are KDE Neon GNU/Linux & GNU/Linux Mint (what a mess! I administer the former for users and used to administer the latter) and in the past some similar miscellaneous ones, and Gentoo GNU/Linux, all which chroot fine even to use network and update those OS... however after successfully installing Fedora and openSUSE (what a mess!) and running bash on them, then rebooting into Slackware (and similarly mounting /dev, /proc, /sys in a way which works for all others) the following happens.

Code:

root@cosmos:~# chroot /fedora
chroot: failed to run command ‘/bin/bash’: Permission denied
root@cosmos:~# chroot /suse
chroot: failed to run command ‘/bin/bash’: Permission denied

Perhaps the question is more suited to their forums, but what could be the cause of this? I wonder if it has to do with whether they use SELinux or this depends on 'running some service (systemd)', etc.
        If this works with debootstrap I'd just like to see it eventually work with all major GNU/Linux. Chroot is good for command-line stuff but can be hard to configure X to work right, for which people suggested using virtual machines (VMs) which I'd like to learn how to use these partitions for those in (A)QEMU. In the past I used Xen (it'd be nice to do similar with *BSD and be able to switch there from Slackware) but it was difficult to keep updated and I don't know you could run X sessions in that unless they were separate (unlike Qubes which uses Xen to run programs from each OS in one X session but is extremely security-focused (for activists, etc.) to a point it can be impractical for average people who don't need that to an extreme level, like doesn't let you use network in 'DOM0').

nobodino · 06-01-2023, 05:47 AM

I can help you with I do with SFS:

Code:

# mkidir /mnt/sfs
# mount -t auto /dev/sda2 /mnt/sfs
# export SFS=/mnt/sfs
#  echo $SFS
# cd /mnt

copy the 2 following scripts under /mnt

Code:

#!/bin/bash
mount -v --bind /dev "$SFS"/dev
mount -vt devpts devpts "$SFS"/dev/pts -o gid=5,mode=620
mount -vt proc proc "$SFS"/proc
mount -vt sysfs sysfs "$SFS"/sys
mount -vt tmpfs tmpfs "$SFS"/run
if [ -h "$SFS"/dev/shm ]; then
  mkdir -pv "$SFS"/"$(readlink "$SFS"/dev/shm)"
fi

Code:

#!/bin/sh
chroot "$SFS" /usr/bin/env -i HOME=/root TERM="$TERM" PS1='\u:\w\$ ' PATH=/bin:/usr/bin:/sbin:/usr/sbin /bin/bash --login

then execute them:

Code:

# chmod +x *.sh
# ./mount-sfs
# ./chroot1

And here you are in the chrooted environnement.

I just tried it with linux-mint now.

dchmelik · 06-01-2023, 06:02 AM

I prefer to mount as I've learned with Slackware, which is usually with '-o bind', not '-vt', which I don't recall what that does differently, but I read some OS need a 'remount' line as shown in what I use below... I'd just forgotten to try the remount line with openSUSE, Fedora but now did and they now chroot fine.

Code:

mount -o bind /dev /neon/dev                                                                                                                  
mount -o bind /proc /neon/proc                                                                                                                
mount -o bind /sys /neon/sys                                                                                                                  
mount -o remount,dev,exec /neon                                                                                                               
mount -o bind /dev /mint/dev                                                                                                                  
mount -o bind /proc /mint/proc                                                                                                                
mount -o bind /sys /mint/sys                                                                                                                  
mount -o remount,dev,exec /mint                                                                                                               
mount -o bind /dev /fedora/dev                                                                                                                
mount -o bind /proc /fedora/proc                                                                                                              
mount -o bind /sys /fedora/sys                                                                                                                
mount -o remount,dev,exec /fedora                                                                                                             
mount -o bind /dev /suse/dev                                                                                                                  
mount -o bind /proc /suse/proc                                                                                                                
mount -o bind /sys /suse/sys                                                                                                                  
mount -o remount,dev,exec /suse                                                                                                               
mount -o bind /dev /gentoo/dev                                                                                                                
mount -o bind /proc /gentoo/proc                                                                                                              
mount -o bind /sys /gentoo/sys                                                                                                                
mount -o remount,dev,exec /gentoo

I'm not marking this solved without some more discussion of how to run X (or Wayland) in some of these, preferably with chroot, optionally with Xen, and least preferably (but acceptable) with virtual machines (VM) using these installations on their partitions... I want it done one of these ways to make copying easier when I'm not using them. VM is least preferable because you have to press buttons to get the mouse back out.

notzed · 06-04-2023, 08:01 PM

This is the script I use for a chroot gentoo that I use to build the packages for a slower system. I only really run emerge from it though.

Code:

#!/bin/sh
mount /dev/nvme1n1p2 /mnt/gentoo
mount /dev/nvme1n1p1 /mnt/gentoo/boot

pushd /mnt/gentoo

mount --types proc /proc /mnt/gentoo/proc
mount --rbind /sys /mnt/gentoo/sys
mount --rbind /dev /mnt/gentoo/dev
mount --bind /run /mnt/gentoo/run

echo "Enter chroot environment"
unshare -u chroot /mnt/gentoo /bin/bash

echo "Back home"
popd
umount -l /mnt/gentoo/dev{/shm,/pts,}
umount -R /mnt/gentoo

dchmelik · 06-12-2023, 08:10 PM

Quote:

Originally Posted by notzed

This is the script I use for a chroot gentoo that I use to build the packages for a slower system. I only really run emerge from it though. [...]

That is interesting. What's the purpose of other mount arguments/flags/switches than ones given on docs.slackware.com; do they work better?

rkelsen · 06-13-2023, 12:05 AM

Something else you might consider:

Code:

tail -n +6 /var/lib/pkgtools/packages/lxc* | head -n 11

There has been a ton of development in that space over the past 10-odd years.