diff --git a/build-baremetal b/build-baremetal
index 74d148a..b0c0126 100755
--- a/build-baremetal
+++ b/build-baremetal
@@ -36,7 +36,7 @@ class BaremetalComponent(common.Component):
             uart_address = 0x09000000
         os.makedirs(build_dir, exist_ok=True)
         os.makedirs(common.baremetal_build_lib_dir, exist_ok=True)
-        assert common.run_cmd(
+        common.run_cmd(
             [gcc] +
             cflags +
             [
@@ -44,8 +44,8 @@ class BaremetalComponent(common.Component):
                 '-o', bootloader_obj,
                 os.path.join(common.baremetal_src_lib_dir, '{}{}'.format(args.arch, common.asm_ext)),
             ]
-        ) == 0
-        assert common.run_cmd(
+        )
+        common.run_cmd(
             [gcc] +
             cflags +
             [
@@ -55,7 +55,7 @@ class BaremetalComponent(common.Component):
                 '-o', common_obj,
                 os.path.join(common.baremetal_src_lib_dir, 'common' + common.c_ext),
             ]
-        ) == 0
+        )
         self._build_dir(
             '',
             gcc=gcc,
@@ -126,7 +126,7 @@ Build the baremetal examples with crosstool-NG.
             if os.path.isfile(in_path) and os.path.splitext(in_basename)[1] in (common.c_ext, common.asm_ext):
                 in_name = os.path.splitext(in_basename)[0]
                 main_obj = os.path.join(common.baremetal_build_dir, subpath, '{}{}'.format(in_name, common.obj_ext))
-                assert common.run_cmd(
+                common.run_cmd(
                     [gcc] +
                     cflags +
                     [
@@ -134,8 +134,8 @@ Build the baremetal examples with crosstool-NG.
                         '-o', main_obj,
                         os.path.join(common.baremetal_src_dir, in_path),
                     ]
-                ) == 0
-                assert common.run_cmd(
+                )
+                common.run_cmd(
                     [gcc] +
                     cflags +
                     [
@@ -148,7 +148,7 @@ Build the baremetal examples with crosstool-NG.
                         common_obj,
                         main_obj,
                     ]
-                ) == 0
+                )
 
 if __name__ == '__main__':
     BaremetalComponent().build()
diff --git a/build-buildroot b/build-buildroot
index 8f459fb..0592760 100755
--- a/build-buildroot
+++ b/build-buildroot
@@ -133,7 +133,7 @@ usually extra Buildroot targets.
                 if os.path.isdir(package_dir_abs):
                     br2_external_dirs.append(self._path_relative_to_buildroot(package_dir_abs))
             br2_external_str = ':'.join(br2_external_dirs)
-            assert common.run_cmd(
+            common.run_cmd(
                 [
                     'make',
                     'O={}'.format(common.buildroot_build_dir),
@@ -141,7 +141,7 @@ usually extra Buildroot targets.
                     defconfig,
                 ],
                 cwd=common.buildroot_src_dir,
-            ) == 0
+            )
             buildroot_configs = args.buildroot_config
             buildroot_configs.extend([
                 'BR2_JLEVEL={}'.format(nproc),
@@ -241,20 +241,20 @@ usually extra Buildroot targets.
                 buildroot_kernel_config_fragment_str = 'BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES="{}"'.format(' '.join(kernel_config_fragments))
                 buildroot_configs.append(buildroot_kernel_config_fragment_str)
                 common.write_configs(common.buildroot_config_file, buildroot_configs, buildroot_config_fragments)
-                assert common.run_cmd(
+                common.run_cmd(
                     [
                         'make',
                         'O={}'.format(common.buildroot_build_dir),
                         'olddefconfig',
                     ],
                     cwd=common.buildroot_src_dir,
-                ) == 0
+                )
 
         # Do the actual build.
         common.make_build_dirs()
         if not args.no_all:
             extra_make_args.append('all')
-        assert common.run_cmd(
+        common.run_cmd(
             [
                 'make',
                 'LKMC_GEM5_SRCDIR="{}"'.format(common.gem5_src_dir),
@@ -267,7 +267,7 @@ usually extra Buildroot targets.
             out_file=os.path.join(common.buildroot_build_dir, 'lkmc.log'),
             delete_env=['LD_LIBRARY_PATH'],
             cwd=common.buildroot_src_dir,
-        ) == 0
+        )
 
         # Create the qcow2 from ext2.
         # Skip if qemu is not present, because gem5 does not need the qcow2.
diff --git a/build-crosstool-ng b/build-crosstool-ng
index 75602a7..07ae78c 100755
--- a/build-crosstool-ng
+++ b/build-crosstool-ng
@@ -17,22 +17,22 @@ class CrosstoolNgComponent(common.Component):
         # Bootstrap out-ot-tree WONTFIX. I've tried.
         # https://github.com/crosstool-ng/crosstool-ng/issues/1021
         os.chdir(common.crosstool_ng_src_dir)
-        assert common.run_cmd(
+        common.run_cmd(
             [os.path.join(common.crosstool_ng_src_dir, 'bootstrap')],
-        ) == 0
+        )
         os.chdir(common.crosstool_ng_util_dir)
-        assert common.run_cmd(
+        common.run_cmd(
             [
                 os.path.join(common.crosstool_ng_src_dir, 'configure'),
                 '--enable-local',
             ],
-        ) == 0
-        assert common.run_cmd(
+        )
+        common.run_cmd(
             [
                 'make',
                 '-j', str(nproc),
             ],
-        ) == 0
+        )
 
         # Build the toolchain.
         common.cp(
@@ -47,14 +47,14 @@ class CrosstoolNgComponent(common.Component):
                 'CT_LOCAL_TARBALLS_DIR="{}"'.format(common.crosstool_ng_download_dir),
             ]
         )
-        assert common.run_cmd(
+        common.run_cmd(
             [
                 common.crosstool_ng_executable,
                 'defconfig',
             ],
-        ) == 0
+        )
         os.unlink(defconfig_dest)
-        assert common.run_cmd(
+        common.run_cmd(
             [
                 common.crosstool_ng_executable,
                 'build',
@@ -63,7 +63,7 @@ class CrosstoolNgComponent(common.Component):
             out_file=os.path.join(build_dir, 'lkmc.log'),
             delete_env=['LD_LIBRARY_PATH'],
             extra_paths=[common.ccache_dir],
-        ) == 0
+        )
 
     def get_argparse_args(self):
         return {
diff --git a/build-docker b/build-docker
index 9ad7444..4e4063f 100755
--- a/build-docker
+++ b/build-docker
@@ -31,12 +31,12 @@ if not args.clean:
             '--format', '{{.Names}}',
     ]).decode()
     if container_name in containers.split():
-        assert common.run_cmd([
+        common.run_cmd([
             'docker',
             'rm',
             container_name,
-        ]) == 0
-    assert common.run_cmd([
+        ])
+    common.run_cmd([
         'docker',
         'create',
         '--name', container_name,
@@ -49,27 +49,27 @@ if not args.clean:
         '-v', '{}:{}'.format(common.root_dir, target_dir),
         'ubuntu:18.04',
         'bash',
-    ]) == 0
-    assert common.run_cmd([
+    ])
+    common.run_cmd([
         'docker',
         'export',
         '-o',
         common.docker_tar_file,
         container_name,
-    ]) == 0
+    ])
     tar = tarfile.open(common.docker_tar_file)
     tar.extractall(common.docker_tar_dir)
     tar.close()
     # sudo not required in theory
     # https://askubuntu.com/questions/1046828/how-to-run-libguestfs-tools-tools-such-as-virt-make-fs-without-sudo
-    assert common.run_cmd([
+    common.run_cmd([
         'virt-make-fs',
         '--format', 'raw',
         '--size', '+1G',
         '--type', 'ext2',
         common.docker_tar_dir,
         common.docker_rootfs_raw_file,
-    ]) == 0
+    ])
     common.raw_to_qcow2(prebuilt=True)
     end_time = time.time()
     common.print_time(end_time - start_time)
diff --git a/build-gem5 b/build-gem5
index cae8134..2097ac5 100755
--- a/build-gem5
+++ b/build-gem5
@@ -27,13 +27,13 @@ class Gem5Component(common.Component):
             if not os.path.exists(os.path.join(common.gem5_src_dir, '.git')):
                 if common.gem5_src_dir == common.gem5_default_src_dir:
                     raise Exception('gem5 submodule not checked out')
-                assert common.run_cmd([
+                common.run_cmd([
                     'git',
                     '-C', common.gem5_default_src_dir,
                     'worktree', 'add',
                     '-b', os.path.join('wt', args.gem5_build_id),
                     common.gem5_src_dir
-                ]) == 0
+                ])
         if args.verbose:
             verbose = ['--verbose']
         else:
@@ -44,7 +44,7 @@ class Gem5Component(common.Component):
                 zeroes = b'\x00' * (2 ** 16)
                 for i in range(2 ** 10):
                     dummy_img_file.write(zeroes)
-            assert common.run_cmd(['mkswap', dummy_img_path]) == 0
+            common.run_cmd(['mkswap', dummy_img_path])
             with open(os.path.join(binaries_dir, 'x86_64-vmlinux-2.6.22.9'), 'w'):
                 # This file must always be present, despite --kernel overriding that default and selecting the kernel.
                 # I'm not even joking. No one has ever built x86 gem5 without the magic dist dir present.
@@ -55,7 +55,7 @@ class Gem5Component(common.Component):
             # dtb
             dt_src_dir = os.path.join(gem5_system_src_dir, 'arm', 'dt')
             dt_build_dir = os.path.join(common.gem5_system_dir, 'arm', 'dt')
-            assert common.run_cmd(['make', '-C', dt_src_dir]) == 0
+            common.run_cmd(['make', '-C', dt_src_dir])
             os.makedirs(dt_build_dir, exist_ok=True)
             for dt in glob.glob(os.path.join(dt_src_dir, '*.dtb')):
                 common.cp(dt, dt_build_dir)
@@ -63,16 +63,16 @@ class Gem5Component(common.Component):
             # Bootloader 32.
             bootloader32_dir = os.path.join(gem5_system_src_dir, 'arm', 'simple_bootloader')
             # TODO use the buildroot cross compiler here, and remove the dependencies from configure.
-            assert common.run_cmd(['make', '-C', bootloader32_dir]) == 0
+            common.run_cmd(['make', '-C', bootloader32_dir])
             # bootloader
             common.cp(os.path.join(bootloader32_dir, 'boot_emm.arm'), binaries_dir)
 
             # Bootloader 64.
             bootloader64_dir = os.path.join(gem5_system_src_dir, 'arm', 'aarch64_bootloader')
             # TODO cross_compile is ignored because the make does not use CC...
-            assert common.run_cmd(['make', '-C', bootloader64_dir]) == 0
+            common.run_cmd(['make', '-C', bootloader64_dir])
             common.cp(os.path.join(bootloader64_dir, 'boot_emm.arm64'), binaries_dir)
-        assert common.run_cmd(
+        common.run_cmd(
             (
                 [
                     'scons',
@@ -85,10 +85,10 @@ class Gem5Component(common.Component):
             ),
             cwd=common.gem5_src_dir,
             extra_paths=[common.ccache_dir],
-        ) == 0
+        )
         term_src_dir = os.path.join(common.gem5_src_dir, 'util/term')
         m5term_build = os.path.join(term_src_dir, 'm5term')
-        assert common.run_cmd(['make', '-C', term_src_dir]) == 0
+        common.run_cmd(['make', '-C', term_src_dir])
         if os.path.exists(common.gem5_m5term):
             # Otherwise common.cp would fail with "Text file busy" if you
             # tried to rebuild while running m5term:
diff --git a/build-linux b/build-linux
index c2269ca..d4934ab 100755
--- a/build-linux
+++ b/build-linux
@@ -43,7 +43,7 @@ class LinuxComponent(common.Component):
             verbose = ['V=1']
         else:
             verbose = []
-        assert common.run_cmd(
+        common.run_cmd(
             [
                 os.path.join(common.linux_src_dir, 'scripts', 'kconfig', 'merge_config.sh'),
                 '-m',
@@ -52,8 +52,8 @@ class LinuxComponent(common.Component):
                 os.path.join(common.linux_config_dir, 'min'),
                 os.path.join(common.linux_config_dir, 'default'),
             ],
-        ) == 0
-        assert common.run_cmd(
+        )
+        common.run_cmd(
             (
                 [
                     'make',
@@ -65,8 +65,8 @@ class LinuxComponent(common.Component):
                 ]
             ),
             **common_args,
-        ) == 0
-        assert common.run_cmd(
+        )
+        common.run_cmd(
             (
                 [
                     'make',
@@ -77,7 +77,7 @@ class LinuxComponent(common.Component):
                 args.extra_make_args
             ),
             **common_args,
-        ) == 0
+        )
 
     def get_argparse_args(self):
         return {
diff --git a/build-m5 b/build-m5
index c15ebd5..ce886a3 100755
--- a/build-m5
+++ b/build-m5
@@ -28,19 +28,19 @@ class M5Component(common.Component):
 
     def do_build(self, args):
         os.makedirs(common.gem5_m5_build_dir, exist_ok=True)
-        assert common.run_cmd(
+        common.run_cmd(
             self.get_make_cmd(args),
             cwd=common.gem5_m5_src_dir,
-        ) == 0
+        )
         print(common.out_rootfs_overlay_bin_dir)
         os.makedirs(common.out_rootfs_overlay_bin_dir, exist_ok=True)
         common.cp(os.path.join(common.gem5_m5_src_dir, 'm5'), common.out_rootfs_overlay_bin_dir)
 
     def clean(self, args):
-        assert common.run_cmd(
+        common.run_cmd(
             self.get_make_cmd(args) + ['clean'],
             cwd=common.gem5_m5_src_dir,
-        ) == 0
+        )
 
 if __name__ == '__main__':
     M5Component().build()
diff --git a/build-modules b/build-modules
index b3e14f0..2d83ca2 100755
--- a/build-modules
+++ b/build-modules
@@ -79,7 +79,7 @@ class ModulesComponent(common.Component):
         else:
             linux_dir = common.linux_build_dir
         build_subdir = os.path.join(build_dir, common.kernel_modules_subdir)
-        assert common.run_cmd(
+        common.run_cmd(
             (
                 [
                     'make',
@@ -94,7 +94,7 @@ class ModulesComponent(common.Component):
                 verbose
             ),
             cwd=os.path.join(build_subdir),
-        ) == 0
+        )
         common.copy_dir_if_update_non_recursive(
             srcdir=build_subdir,
             destdir=common.out_rootfs_overlay_dir,
diff --git a/build-qemu b/build-qemu
index f8cfbe2..2caef78 100755
--- a/build-qemu
+++ b/build-qemu
@@ -22,7 +22,7 @@ class QemuComponent(common.Component):
             verbose = ['V=1']
         else:
             verbose = []
-        assert common.run_cmd(
+        common.run_cmd(
             [
                 os.path.join(common.qemu_src_dir, 'configure'),
                 '--enable-debug',
@@ -34,8 +34,8 @@ class QemuComponent(common.Component):
             args.extra_config_args,
             extra_paths=[common.ccache_dir],
             cwd=build_dir
-        ) == 0
-        assert common.run_cmd(
+        )
+        common.run_cmd(
             (
                 [
                     'make',
@@ -46,7 +46,7 @@ class QemuComponent(common.Component):
             ),
             cwd=build_dir,
             extra_paths=[common.ccache_dir],
-        ) == 0
+        )
 
     def get_build_dir(self, args):
         return common.qemu_build_dir
diff --git a/build-userland b/build-userland
index 44a0396..872bc95 100755
--- a/build-userland
+++ b/build-userland
@@ -38,7 +38,7 @@ has the OpenBLAS libraries and headers installed.
         allowed_toolchains = ['buildroot']
         cc = common.get_toolchain_tool('gcc', allowed_toolchains=allowed_toolchains)
         cxx = common.get_toolchain_tool('g++', allowed_toolchains=allowed_toolchains)
-        assert common.run_cmd(
+        common.run_cmd(
             (
                 [
                     'make',
@@ -54,7 +54,7 @@ has the OpenBLAS libraries and headers installed.
             ),
             cwd=common.userland_src_dir,
             extra_paths=[common.ccache_dir],
-        ) == 0
+        )
         common.copy_dir_if_update_non_recursive(
             srcdir=build_dir,
             destdir=common.out_rootfs_overlay_dir,
diff --git a/common.py b/common.py
index b465690..d2c2926 100644
--- a/common.py
+++ b/common.py
@@ -415,13 +415,10 @@ def make_run_dirs():
     os.makedirs(this_module.p9_dir, exist_ok=True)
     os.makedirs(this_module.qemu_run_dir, exist_ok=True)
 
-def print_cmd(cmd, cwd=None, cmd_file=None, extra_env=None, extra_paths=None):
+def cmd_to_string(cmd, cwd=None, extra_env=None, extra_paths=None):
     '''
     Format a command given as a list of strings so that it can
     be viewed nicely and executed by bash directly and print it to stdout.
-
-    Optionally save the command to cmd_file file, and add extra_env
-    environment variables to the command generated.
     '''
     newline_separator = ' \\\n'
     out = []
@@ -435,12 +432,21 @@ def print_cmd(cmd, cwd=None, cmd_file=None, extra_env=None, extra_paths=None):
         out.append('{}={}'.format(shlex.quote(key), shlex.quote(extra_env[key])) + newline_separator)
     for arg in cmd:
         out.append(shlex.quote(arg) + newline_separator)
-    out = '  '.join(out) + ';\n'
-    print(this_module.command_prefix + out, end='')
+    return '  '.join(out) + ';\n'
+
+def print_cmd(cmd, cwd=None, cmd_file=None, extra_env=None, extra_paths=None):
+    '''
+    Print cmd_to_string to stdout.
+
+    Optionally save the command to cmd_file file, and add extra_env
+    environment variables to the command generated.
+    '''
+    cmd_string = cmd_to_string(cmd, cwd=None, extra_env=None, extra_paths=None)
+    print(this_module.command_prefix + cmd_string, end='')
     if cmd_file is not None:
         with open(cmd_file, 'w') as f:
             f.write('#!/usr/bin/env bash\n')
-            f.write(out)
+            f.write(cmd_string)
         st = os.stat(cmd_file)
         os.chmod(cmd_file, st.st_mode | stat.S_IXUSR)
 
@@ -466,7 +472,7 @@ def raw_to_qcow2(prebuilt=False, reverse=False):
         tmp = infile
         infile = outfile
         outfile = tmp
-    assert this_module.run_cmd([
+    this_module.run_cmd([
         qemu_img_executable,
         # Prevent qemu-img from generating trace files like QEMU. Disgusting.
         '-T', 'pr_manager_run,file=/dev/null',
@@ -475,7 +481,7 @@ def raw_to_qcow2(prebuilt=False, reverse=False):
         '-O', outfmt,
         infile,
         outfile,
-    ]) == 0
+    ])
 
 def raise_no_x86(arch):
     if (arch == 'x86_64'):
@@ -508,6 +514,7 @@ def run_cmd(
         extra_paths=None,
         delete_env=None,
         dry_run=False,
+        raise_on_failure=True,
         **kwargs
     ):
     '''
@@ -598,7 +605,10 @@ def run_cmd(
                             break
         signal.signal(signal.SIGINT, sigint_old)
         #signal.signal(signal.SIGPIPE, sigpipe_old)
-        return proc.returncode
+        returncode = proc.returncode
+        if returncode != 0 and raise_on_failure:
+            raise Exception('Command exited with status: {}'.format(returncode))
+        return returncode
     else:
         return 0
 
diff --git a/run b/run
index b463de9..6c7381a 100755
--- a/run
+++ b/run
@@ -118,7 +118,7 @@ def main(args, extra_args=None):
             # This is to run gem5 from a prebuilt download.
             if (not args.baremetal is None) or (not os.path.exists(common.linux_image)):
                 raise_image_not_found()
-            assert common.run_cmd([os.path.join(common.extract_vmlinux, common.linux_image)]) == 0
+            common.run_cmd([os.path.join(common.extract_vmlinux, common.linux_image)])
         os.makedirs(os.path.dirname(common.gem5_readfile), exist_ok=True)
         with open(common.gem5_readfile, 'w') as readfile:
             readfile.write(args.gem5_readfile)
@@ -313,10 +313,7 @@ def main(args, extra_args=None):
         out_file = None
     else:
         out_file = common.termout_file
-    returncode = common.run_cmd(cmd, cmd_file=common.run_cmd_file, out_file=out_file, extra_env=extra_env)
-    if returncode != 0:
-        common.log_error('simulator exited with status != 0')
-        return returncode
+    common.run_cmd(cmd, cmd_file=common.run_cmd_file, out_file=out_file, extra_env=extra_env)
     # Check if guest panicked.
     if args.gem5:
         # We have to do some parsing here because gem5 exits with status 0 even when panic happens.