lib: Remove User-Mode Linux

User-Mode Linux was an alternative hypervisor that could run the
appliance, instead of using qemu.  It had many limitations including
lack of network, and UML support in Linux has been semi-broken for a
long time.  It was also slower than KVM on baremeal in general and had
various corner cases which were much slower including the emulated
serial port which made bulk uploads and downloads painful.  Also of
course it lacked qemu-specific features like qcow2 or any
network-backed disk, so many disk images could not be opened this way.

This was never supported in RHEL.

See-also: https://bugzilla.redhat.com/1144197

tests/c-api/test-add-libvirt-dom.c

@@ -73,7 +73,6 @@ main (int argc, char *argv[])
   virDomainPtr dom;
   virErrorPtr err;
   int r;
-  char *backend;
   char cwd[1024];
   FILE *fp;
   char libvirt_uri[sizeof cwd + 64];
@@ -86,13 +85,6 @@ main (int argc, char *argv[])
   if (g == NULL)
     error (EXIT_FAILURE, errno, "guestfs_create");
 
-  backend = guestfs_get_backend (g);
-  if (STREQ (backend, "uml")) {
-    free (backend);
-    error (77, 0, "test skipped because UML backend does not support qcow2");
-  }
-  free (backend);
-
   /* Create the libvirt XML and test images in the current
    * directory.
    */

tests/disk-labels/test-disk-labels.pl

@@ -25,11 +25,6 @@ use Sys::Guestfs;
 
 exit 77 if $ENV{SKIP_TEST_DISK_LABELS_PL};
 
-if (Sys::Guestfs->new()->get_backend() eq "uml") {
-    print "$0: test skipped because UML backend does not support disk labels\n";
-    exit 77
-}
-
 my $g = Sys::Guestfs->new ();
 
 # Add two drives.

tests/md/test-inspect-fstab.sh

@@ -24,7 +24,6 @@ set -e
 $TEST_FUNCTIONS
 skip_because "device name hints are broken" ;# XXX Fix before 1.38
 skip_if_skipped
-skip_if_backend uml
 skip_unless_phony_guest fedora.img
 
 canonical="sed -r s,/dev/[abce-ln-z]+d,/dev/sd,g"

tests/mountable/test-mountable-inspect.sh

@@ -20,7 +20,6 @@ set -e
 
 $TEST_FUNCTIONS
 skip_if_skipped
-skip_if_backend uml
 skip_unless_feature_available btrfs
 
 canonical="sed s,/dev/vd,/dev/sd,g"

tests/nbd/test-nbd.pl

@@ -27,11 +27,6 @@ END { kill 15, $pid if $pid > 0 };
 
 exit 77 if $ENV{SKIP_TEST_NBD_PL};
 
-if (Sys::Guestfs->new()->get_backend() eq "uml") {
-    print "$0: test skipped because UML backend does not support NBD\n";
-    exit 77
-}
-
 # Check we have qemu-nbd.
 if (system ("qemu-nbd --help >/dev/null 2>&1") != 0) {
     print "$0: test skipped because qemu-nbd program not found\n";

tests/network/test-network.sh

@@ -24,6 +24,5 @@ set -e
 
 $TEST_FUNCTIONS
 skip_if_skipped
-skip_if_backend uml
 
 guestfish --network -a /dev/null run

tests/qemu/qemu-force-tcg.sh

@@ -20,8 +20,6 @@
 
 $TEST_FUNCTIONS
 skip_if_skipped
-# Only applicable if the backend uses qemu.
-skip_if_backend uml
 
 set -e
 

tests/qemu/qemu-snapshot-isolation-qcow2.sh

@@ -24,8 +24,6 @@ set -e
 
 $TEST_FUNCTIONS
 skip_if_skipped
-# UML backend doesn't support qcow2 format.
-skip_if_backend uml
 
 f=isolation-qcow2.img
 rm -f $f

tests/regressions/rhbz1370424.sh

@@ -24,7 +24,6 @@ set -e
 
 $TEST_FUNCTIONS
 skip_if_skipped
-skip_if_backend uml
 
 guestfish <<EOF
 -add-domain rhbz1370424 \

tests/regressions/rhbz690819.sh

@@ -31,8 +31,6 @@ skip_if_arch ppc64
 skip_if_arch ppc64le
 skip_if_arch s390x
 skip_if_backend libvirt
-# UML doesn't support the 'iface' parameter.
-skip_if_backend uml
 
 rm -f rhbz690819.img
 

tests/regressions/rhbz975797.sh

@@ -31,8 +31,6 @@ skip_if_arch ppc64
 skip_if_arch ppc64le
 skip_if_arch s390x
 skip_if_backend libvirt
-# UML doesn't support the 'iface' parameter.
-skip_if_backend uml
 
 rm -f rhbz975797-*.img
 

tests/relative-paths/test-relative-paths.sh

@@ -21,10 +21,6 @@ set -e
 $TEST_FUNCTIONS
 skip_if_skipped
 
-# UML doesn't support qcow2.  Conceivably there might be a similar
-# problem with UML COW images which would require a separate test.
-skip_if_backend uml
-
 rm -f backing*
 rm -f overlay*
 rm -f link*

tests/rsync/test-rsync.sh

@@ -44,10 +44,6 @@ case "$backend" in
         echo "$0: skipping test because host firewall will probably prevent this test from working"
         exit 77
         ;;
-    uml)
-        echo "$0: skipping test because networking is not available in the UML backend"
-        exit 77
-        ;;
     *)
         echo "$0: don't know how to get IP address of backend $backend"
         exit 77

tests/test-functions.sh

@@ -54,7 +54,7 @@ skip_if_skipped ()
 }
 
 # Skip if the current libguestfs backend is $1.
-# eg. skip_if_backend uml
+# eg. skip_if_backend libvirt
 skip_if_backend ()
 {
     local b="$(guestfish get-backend)"