QEMU/KVM with Virt-Manager is a great alternative to Virtualbox. Virt-Manager depends on libvirt, so overall this alternative far exceeds Virtualbox, and it is not difficult to get this working. This is suppose to be a clear and reproducible path to get Virt-Manage with all those components installed on Slackware 15.0 and beyond. It is suppose to be newbie friendly “step-by-step”. QEMU-6.2.0 and libvirt-8.0.0 can both be built and installed from source on Slackware 15.0 out of the box without any issues, but might be missing some functions you would want. This guide could also be a reference to some of those optional dependencies.

Be sure to use Slackware 15.0 and Kernel-generic to accurately be able to reproduce this build and as a reference point. It should work on others, but use kernel-generic to be sure. Your processor must be capable of virtualization. You can check that with:

lscpu | grep -i virtualization

It should give an answer like:

 Virtualization:                  VT-x

For amd it will give another answer like “AMD-v”.

Before installation it is possible to dry run ./configure for qemu and meson-build for libvirt and you will find this info: (not complete)
qemu says:

• Run-time dependency libnfs found: NO / libnfs support: NO
  
• Run-time dependency spice-protocol found: NO / spice protocol support: NO\
  
• Run-time dependency spice-server found: NO
  
• Run-time dependency virglrenderer found: NO / virgl support: NO
  
• vde support: NO
  
• usb net redir: NO
  

libvirt says:

• Library numa found: NO (numactl: NO)
  
• Run-time dependency yajl found: NO (yajl: NO)
  

1. You CAN use “make install” or equivalent if you want (maybe “DESTDIR=/opt install” if you want to install directly in /opt), but for ease and stages, use the above method instead. (building_a_package)
2. This guide is using /opt/root/build for user (with user read/write access) - you could/should use /home/user/build (simply replace all “/opt/root” in the steps of this guide with “/home/user” ←- where “user” is your username)
3. This guide is using /opt/fakeroot for root and DESTDIR for packaging - you could use that or another root only writable directory (root root 755). If you're unsure, use /opt/fakeroot so you can follow step-by-step.
4. Whenever it says “(as ROOT)” you must continue in the same folder you were in (su)
5. Whenever it says “(as USER)” or “(as ROOT)”, it is a note, there are also some other notes in (paranthesis) inside code brackets
6. As this guide moves on, it will repeat less and less assumed details (see stage1 for most details)

• Audit support (general) - if you habitually use this and/or might need it, better to do it now before kvm/qemu/libvirt
• Gstreamer codecs (spice) - libav and gst-plugins-ugly support, better to deal with general codec stuff before qemu/spice etc, in particular those 2
  • https://gstreamer.freedesktop.org/src/gst-plugins-ugly/gst-plugins-ugly-1.18.5.tar.xz
  • https://gstreamer.freedesktop.org/src/gst-libav/gst-libav-1.18.5.tar.xz
• Compiling Qemu with only the machines you need (unless you need alot of exotic CPU emulation and/or cross-compilation)

cd /opt/root/build
mkdir stage1 stage2 stage3 stage4 stage5 stage6

(hard dependencies of stage2)
https://gitlab.com/libosinfo/libosinfo/-/tags/v1.9.0 (dependency of virt-manager)
https://gitlab.com/libosinfo/osinfo-db-tools/-/tags/v1.9.0 (dependency of virt-manager and osinfo-db)
https://gitlab.com/spice/spice-protocol/-/tags/v0.14.3 (dependency of spice)
Hint. the download button is on the upper right side of the screen.

Download and put the packages in your stage1 build directory.

(as USER)
cd /opt/root/build/stage1/
tar -xvf libosinfo-v1.9.0.tar.gz && tar -xvf osinfo-db-tools-v1.9.0.tar.gz && tar -xvf spice-protocol-v0.14.3.tar.gz

Note. “meson configure” is optional
libosinfo-v1.9.0

(as USER)
cd libosinfo-v1.9.0
meson configure
meson build
ninja -C build
(as ROOT)
DESTDIR=/opt/fakeroot ninja -C build install

osinfo-db-tools-v1.9.0 (follow process 1)
spice-protocol-v0.14.3 (process 1)
Note. spice-protocol comes without install instructions, and acts strange, but you can still follow process 1, it will work correctly. (ignore the warnings)

(as ROOT still)

cd /opt/fakeroot
mkdir -p usr/lib64/girepository-1.0
mv usr/local/lib64/girepository-1.0/* usr/lib64/girepository-1.0/
rm -r usr/local/lib64/girepository-1.0

process 2 (see link above “building_a_package”)

strip -s usr/local/bin/* usr/local/lib64/*     (you can skip this)
gzip -9 usr/local/share/man/man1/*             (you can skip this)
mkdir install
nano install/slack-desc
virt-stage1: virt-stage1 (stage1 dependencies for libvirt/qemu/virt-manager)
virt-stage1:
virt-stage1: libosinfo-v1.9.0 and osinfo-db-tools-v1.9.0, spice-protocol-0.15.0
virt-stage1: dependencies for stage 2.
virt-stage1:
ctrl+x "save"

You should probably first check folder and file permissions (for the below step) by running: (hint. it should all be root root)

ls -lhaR

then

makepkg ../virt-stage1_zeebra_s15_64_v1.0.txz (you can name it something else if you want, ending with .txz)

-You will be asked about script/symbolic links, answer “y” for yes
-You will be asked about setting safe permissions, answer “n” for no (if you checked and find no problem)

mkdir /opt/slackpacks
cp ../virt-stage1_zeebra_s15_64_v1.0.txz /opt/slackpacks
cd /opt/slackpacks
installpkg virt-stage1_zeebra_s15_64_v1.0.txz

if something went wrong, you can use:

removepkg virt-stage1_zeebra_s15_64_v1.0.txz

and try whatever necessary steps again.

cd /opt/
mv fakeroot/ stage1-fakeroot
mkdir fakeroot

(some are hard dependencies of stage/step 4 and 6)
https://github.com/dgibson/dtc/releases/tag/v1.6.1 (can be built after qemu according to xiling and can be dropped unless you find you need it after)
https://github.com/sahlberg/libnfs/releases/tag/libnfs-5.0.1 (optional dependency of qemu, may be optional dependency of libvirt)
https://gitlab.com/libosinfo/osinfo-db/-/tags/v20210202 (should be built/imported after osinfo-db-tools, libosinfo is c wrapper for those things)
https://github.com/numactl/numactl/releases/tag/v2.0.14 (optional dependency qemu AND libvirt and possibly some other packages)
https://www.spice-space.org/download/releases/spice-server/ (indirect link - spice is the default display mode of virt-manager for qemu and so a dependency of it)
https://www.spice-space.org/download/releases/spice-server/spice-0.15.0.tar.bz2 (direct link)
https://gitlab.com/spice/usbredir/-/tags/usbredir-0.9.0 (mentioned by several other packages as I remember, hard dependency of some, optional qemu)
https://github.com/virtualsquare/vde-2 (since vde2 release is ancient, I take master from today 06-feb-2022, I would say this is an important function in qemu, but optional )
https://github.com/freedesktop/virglrenderer/releases/tag/0.9.1 (I would say this is an important function in qemu, but optional)
https://github.com/lloyd/yajl/releases/tag/2.1.0 (it would be best to skip this, but for now we include it, libvirt optional dependency)

(as USER)
cd /opt/root/build/stage2

unpack all the files in stage2

tar -xvf dtc-1.6.1.tar.gz && tar -xvf libnfs-libnfs-5.0.1.tar.gz && tar -xvf numactl-2.0.14.tar.gz && tar -xvf osinfo-db-v20210202.tar.gz && tar -xvf spice-0.15.0.tar.bz2 && tar -xvf usbredir-usbredir-0.9.0.tar.gz && unzip vde-2-master.zip && tar -xvf virglrenderer-0.9.1.tar.gz && tar -xvf yajl-2.1.0.tar.gz

So, for the sake of THIS howto, the “GNU process” is as following:

(as USER)
cd packagedir
./configure --libdir=/usr/local/lib64
make
(as ROOT)
make DESTDIR=/opt/fakeroot install

alphabetical: (ls -la)
dtc-1.6.1 (process 1)
libnfs-5.0.1 (GNU process)
exception!! you need to run ./bootstrap before ./configure
numactl-2.0.14 (GNU process)
exception!! you need to run ./autogen.sh before ./configure
osinfo-db-v20210202

(as USER)
cd osinfo-db-v20210202
make -j3 (there is alot to compile here, -j3 is 3 cores, use another number for more/less)
(as ROOT)
mkdir /opt/fakeroot/run
ls (find the name of the osinfo-db-$VERSION.tar.xz database and use THAT in YOUR case, in my example, I'm using the name it tells ME)
cp osinfo-db-20220206.tar.xz /opt/fakeroot/run
cd /opt/fakeroot
mkdir install
nano install/doinst.sh
( osinfo-db-import --local /run/osinfo-db-20220206.tar.xz )
( osinfo-db-validate )
ctrl+x (save)

(yes, the exact 2 lines above should be the content of the file, except the name variable)

cd /opt/root/build/stage2/

spice-0.15.0 (GNU process)
Attention!! Spice also mentions 2 gstreamer codecs. You might want to install those and others before doing libvirt/qemu/virt-manager. You can also do that later and rebuild spice after that.
usbredir-usbredir-0.9.0 (GNU process)
Exception!! You need to run ./autogen.sh before ./configure
vde-2-master (GNU process)
exception!! you need to run autoreconf –install before ./configure
virglrenderer-0.9.1 (process 1)
yajl-2.1.0

(as USER)
cd yajl-2.1.0
./configure
make
(as ROOT)
make DESTDIR=/opt/fakeroot install

yajl doesn't obey –libdir unless done with cmake so do:

mv /opt/fakeroot/usr/local/lib/libyajl* /opt/fakeroot/usr/local/lib64/
rm -r /opt/fakeroot/usr/local/lib

Our stage2 package is now in /opt/fakeroot
Repeat

cd /opt/fakeroot
strip -s usr/local/bin/* usr/local/lib64/*
gzip -9 usr/local/share/man/man1/* usr/local/share/man/man2/* usr/local/share/man/man3/* usr/local/share/man/man8/*
nano install/slack-desc
virt-stage2: virt-stage2 (stage 2 dependencies of qemu/libvirt/virt-manager)
virt-stage2:
virt-stage2: This is a collection of tools and libraries required and/or necessary
virt-stage2: for proper qmeu/libvirt/virt-manager implementation on Slackware 15.
virt-stage2: dtc-1.6.1, libnfs-5.0.1, numactl-2.0.14, osinfo-db-v20210202,
virt-stage2: spice-0.15.0, usbredir-0.9.0, vde-2-master-06-feb-2022,
virt-stage2: virglrenderer-0.9.1, yajl-2.1.0.
virt-stage2: It's the 2nd stage of a series of dependencies.
virt-stage2:
ctrl+x (save)
ls -lhaR
makepkg ../virt-stage2_zeebra_s15_64_v1.0.txz

-You will be asked about symbolic links, answer “y” for yes
-You will be asked about setting safe permissions, answer “n” for no (if you checked and find no problem)

cp ../virt-stage2_zeebra_s15_64_v1.0.txz /opt/slackpacks
cd /opt/slackpacks
installpkg virt-stage2_zeebra_s15_64_v1.0.txz

( process 2 ends here )
You should NOT get an error like this: (Error when getting information for file “/usr/local/etc/osinfo”: No such file or directory), if you do, something went wrong with osinfo database loading, and you can load it manually (see doinst.sh) or fix your package.

after installing this package, we can go to qemu testdir and test with ./configure, we expect this:
libnfs support: Yes
virgl support: Yes
vde support: Yes
spice protocol support: Yes
spice server support: Yes
usb net redir: Yes

we can do the same for libvirt with “meson build” command and we expect this:
numactl: Yes
yajl: Yes

If everything went fine, do some cleaning:

mv /opt/fakeroot /opt/stage2-fakeroot
mkdir /opt/fakeroot

https://libvirt.org/sources/
https://libvirt.org/sources/libvirt-8.0.0.tar.xz

libvirt-8.0.0 (process 1)
Then..

(as ROOT)
cd /opt/fakeroot
mkdir -p /opt/fakeroot/usr/share/polkit-1/actions
mkdir /opt/fakeroot/usr/share/polkit-1/rules.d
mv /opt/fakeroot/usr/local/share/polkit-1/actions/org.libvirt* /opt/fakeroot/usr/share/polkit-1/actions/
mv /opt/fakeroot/usr/local/share/polkit-1/rules.d/50-libvirt.rules /opt/fakeroot/usr/share/polkit-1/rules.d/
rm -rf /opt/fakeroot/usr/local/share/polkit-1

Then repeat process 2 to package and install this. Adapt it to this package. You can use this: (for this package)

strip -s usr/local/bin/* usr/local/lib64/*
gzip -9 usr/local/share/man/man1/* usr/local/share/man/man7/* usr/local/share/man/man8/*

When done with process 2, clean:

cd /opt
mv fakeroot/ libvirt-fakeroot
mkdir fakeroot

(some are hard dependencies of stage/step 6)
https://gitlab.com/libvirt/libvirt-glib/-/tags/v4.0.0 (gobject, gconfig, language bindings, requirement of virt-manager)
https://github.com/libvirt/libvirt-python/releases/tag/v8.0.0 (language bindings, specifically mentioned as build time requirement by virt-manager)
https://download.gnome.org/sources/gtk-vnc/1.3/ (vnc widget“ not sure exactly what this does here, but core c library and python bindings for virt-manager)
https://www.spice-space.org/download/gtk/ (indirect link) (same purpose as the above)
https://www.spice-space.org/download/gtk/spice-gtk-0.39.tar.xz (direct link)

(as USER)
cd /opt/root/build/stage4
tar -xvf gtk-vnc-1.3.0.tar.xz && tar -xvf libvirt-glib-v4.0.0.tar.gz && tar -xvf libvirt-python-8.0.0.tar.gz && tar -xvf spice-gtk-0.39.tar.xz

alphabetical (ls -la)
gtk-vnc-1.3.0 (process 1)
libvirt-glib-v4.0.0 (process 1)
libvirt-python-8.0.0

(as USER)
cd libvirt-python-8.0.0
python3 setup.py build
(I find python messy, so I will do install as user, if you don't, skip to OR as ROOT)
mkdir ../fakeroot
python3 setup.py install --root=/opt/root/build/stage4/fakeroot/
(as ROOT)
cd /opt/root/build/stage4/
chown -R root fakeroot/
chgrp -R root fakeroot/
cd fakeroot/usr/
mv lib64/ /opt/fakeroot/usr/
cd /opt/root/build/stage4/
rm -rf fakeroot

(OR as ROOT)
(python3 setup.py install --root=/opt/fakeroot)

spice-gtk-0.39 (process 1)
Attention: when running “meson build” expect due to stage2 to see this “usbredir: YES”

cd /opt/fakeroot
mkdir -p usr/lib64/girepository-1.0
mv usr/local/lib64/girepository-1.0/* usr/lib64/girepository-1.0/
rm -r usr/local/lib64/girepository-1.0

Then repeat process 2 to package and install this.

Then clean:

cd /opt
mv fakeroot/ stage4-fakeroot
mkdir fakeroot

https://www.qemu.org/ (indirect link)
https://download.qemu.org/qemu-6.2.0.tar.xz (direct link)

QEMU steps will work regardless and doesn't depend on any of these stages. Just not with those wanted functions included in the stages.. QEMU takes a long time to compile unless you compile it with less machines. You should use all processor cores here, so use “make -j4” or however many you have instead of just “make”.

qemu-8.0.0 (GNU Process)

Then repeat process 2 to package and install this.

Clean:

cd /opt
mv fakeroot qemu-fakeroot
mkdir fakeroot

ls configs/targets

Virt-Manager-3.2.0

as USER
cd Virt-Manager-3.2.0
python3 setup.py build
(I find python messy, so I will do install as user, if you don't, skip to OR as ROOT)
mkdir ../fakeroot
python3 setup.py install --root=/opt/root/build/stage6/fakeroot/
as ROOT
mkdir /opt/fakeroot/usr
cd /opt/root/build/stage6/
chown -R root fakeroot/
chgrp -R root fakeroot/
cd fakeroot/usr/
mv bin/ share/ /opt/fakeroot/usr/
cd /opt/root/build/stage6/
rm -rf fakeroot

(OR as ROOT)
(python3 setup.py install --root=/opt/fakeroot)

cd /opt/fakeroot
mkdir install
nano install/doinst.sh
( rm /home/user/.config/dconf/user )
ctrl+x (save)

Note. You don't have to do the above step with doinst.sh, but it will make sure you will not encounter a crash inside virt-manager when you use the function “browse local”. You can do this step manually after instead if you have that error.

Then repeat process 2 to package and install this.

Other packages to consider:

• acpica (acpi tables for qemu)
• ovmf (firmware UEFI stuff for qemu)
• snappy (particular compression algo for qemu)
• gst-plugin-ugly (codec for spice)
• gst-libav (gstreamer codec for spice)
  

If you want configure and set up libvirt/qemu/kvm and virt-manager on Slackware 15.0 use the info in this link:
https://docs.slackware.com/howtos:emulators:libvirt_config_methods

Once you verify that everything is working, you might want to clean up and delete all the fakeroots (/opt/stage1-fakeroot etc) and sources (/opt/root/build/stage1 etc). You only need to keep the resulting slackpacks (/opt/slackpacks)

* Originally written by zeebra

Thanks to truepatriot76 for already having tested a working build and providing a list of dependencies!
Discussions here:
https://www.linuxquestions.org/questions/slackware-14/virt-manager-anyone-got-a-clear-and-working-path-to-this-4175707508/