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Add cross-architecture image build support to imgutil

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Allow building EL and Ubuntu diskless images for a foreign architecture (e.g.
aarch64 on an x86_64 host) by leveraging qemu-user-static. The target
architecture is detected automatically from a -s source tree (for EL),
or may be requested explicitly with the new --arch option.

When the target differs from the host, dnf/debootstrap is invoked with
--forcearch/--arch and the presence of an enabled binfmt_misc handler
with the F (fix-binary) flag is verified up front, so emulation keeps working
inside the installroot chroot and a missing setup yields an actionable
error instead of a confusing exec failure mid-build.

The image architecture is recorded in confluentimg.buildinfo so that
pack selects the initramfs addons for the image architecture rather
than the build host, and exec of a foreign-arch root performs the same
binfmt check.
This commit is contained in:
Markus Hilger
2026-07-09 01:14:33 +02:00
parent 40f1a85932
commit 7633bac055
2 changed files with 173 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files
confluent_client/doc/man/imgutil.ronn
+19
View File
@@ -43,6 +43,16 @@
* `-s`, `--source` <directory>:
Directory to pull installation from, typically a subdirectory of `/var/lib/confluent/distributions`. By default, the repositories for the build system are used. For Ubuntu, this is not supported; the build system repositories are always used.
* `--arch` <architecture>:
Target architecture to build for (`x86_64` or `aarch64`). For Ubuntu, the
Debian-style names `amd64` and `arm64` are accepted as aliases. Building
for a foreign architecture is supported on EL and Ubuntu build hosts and
requires a statically linked qemu-user emulator registered in binfmt_misc
with the F (fix-binary) flag; on Ubuntu this is provided by the
qemu-user-static package (qemu-user-binfmt as of Ubuntu 26.04). For EL,
the architecture is also detected automatically when building from a `-s`
source tree.
* `-y`, `--non-interactive`:
Avoid prompting for confirmation.
@@ -99,6 +109,15 @@ Build a diskless image from a distribution:
imgutil build -s alma-9.6-x86_64 /tmp/myimage
Build an aarch64 EL diskless image on an x86_64 host (the architecture is
detected from the source tree):
imgutil build -s alma-9.6-aarch64 /tmp/myimage
Build an aarch64 Ubuntu diskless image on an amd64 Ubuntu host:
imgutil build --arch aarch64 /tmp/myimage
Execute a shell in an unpacked image:
imgutil exec /tmp/myimage
imgutil/imgutil
+154 -8
View File
@@ -15,7 +15,6 @@ import glob
import json
import argparse
import os
import platform
import pwd
import re
import shutil
@@ -259,7 +258,7 @@ async def capture_remote(args):
os.symlink('/var/lib/confluent/public/site/initramfs.cpio',
os.path.join(outdir, 'boot/initramfs/site.cpio'))
confdir = '/opt/confluent/lib/osdeploy/{}-diskless'.format(oscat)
archaddon = '/opt/confluent/lib/osdeploy/{}-diskless/initramfs/{}/addons.cpio'.format(oscat, platform.machine())
archaddon = '/opt/confluent/lib/osdeploy/{}-diskless/initramfs/{}/addons.cpio'.format(oscat, os.uname().machine)
if os.path.exists(archaddon):
os.symlink(archaddon, os.path.join(outdir, 'boot/initramfs/addons.cpio'))
else:
@@ -462,6 +461,8 @@ def get_mydir(oscategory):
return gencopy
class OsHandler(object):
crossbuild = False
def __init__(self, name, version, arch, args):
self.name = name
self._interactive = True
@@ -496,6 +497,10 @@ class OsHandler(object):
def set_interactive(self, shouldbeinteractive):
self._interactive = shouldbeinteractive
def set_arch(self, arch):
self.arch = arch
self.osname = '{}-{}-{}'.format(self.name, self.version, arch)
def get_json(self):
odata = [self.oscategory, self.version, self.arch, self.name]
for idx in range(len(odata)):
@@ -653,7 +658,22 @@ class SuseHandler(OsHandler):
run_constrainedx(fancy_chroot, (args, self.targpath))
deb_arch_map = {
'aarch64': 'arm64',
'x86_64': 'amd64',
}
uname_arch_map = {
'arm64': 'aarch64',
'amd64': 'x86_64',
}
class DebHandler(OsHandler):
crossbuild = True
def set_arch(self, arch):
super().set_arch(uname_arch_map.get(arch, arch))
def __init__(self, name, version, arch, args, codename, hostpath):
self.includepkgs = []
self.targpath = None
@@ -684,7 +704,10 @@ class DebHandler(OsHandler):
shutil.copytree(srcdir, targdir)
os.chmod(os.path.join(targdir, 'hooks/confluent'), 0o755)
#cmd = ['debootstrap', '--include={0}'.format(','.join(self.includepkgs)), self.codename, self.targpath]
cmd = ['debootstrap', self.codename, self.targpath]
if self.arch != os.uname().machine:
cmd = ['debootstrap', '--arch={0}'.format(deb_arch_map.get(self.arch, self.arch)), self.codename, self.targpath]
else:
cmd = ['debootstrap', self.codename, self.targpath]
subprocess.check_call(cmd)
def _apt(self, args, cmd):
@@ -736,6 +759,8 @@ class DebHandler(OsHandler):
class ElHandler(OsHandler):
crossbuild = True
def __init__(self, name, version, arch, args, hostpath='/'):
self.oscategory = 'el{0}'.format(version.split('.')[0])
self.yumargs = []
@@ -774,7 +799,10 @@ class ElHandler(OsHandler):
self.targpath = targpath
self.yumargs.extend(
['--installroot={0}'.format(targpath),
'--releasever={0}'.format(self.version), 'install'])
'--releasever={0}'.format(self.version)])
if self.arch != os.uname().machine:
self.yumargs.append('--forcearch={0}'.format(self.arch))
self.yumargs.append('install')
def prep_root(self, args):
mkdirp(os.path.join(self.targpath, 'usr/lib/dracut/modules.d'))
@@ -949,6 +977,7 @@ def main():
buildp.add_argument('-a', '--addpackagelist', action='append', default=[],
help='A list of additional packages to include, may be specified multiple times')
buildp.add_argument('-s', '--source', help='Directory to pull installation from, typically a subdirectory of /var/lib/confluent/distributions. By default, the repositories for the build system are used. For Ubuntu, this is not supported, the build system repositories are always used.')
buildp.add_argument('--arch', default=None, help='Target architecture to build for (e.g. aarch64). When it differs from the build host architecture, statically linked qemu-user emulator registered in binfmt_misc with the F flag is required')
buildp.add_argument('-y', '--non-interactive', help='Avoid prompting for confirmation', action='store_true')
buildp.add_argument('-v', '--volume',
help='Directory to make available in the build environment. -v / will '
@@ -992,6 +1021,16 @@ def main():
def exec_root(args):
imgarch = None
try:
with open(os.path.join(args.scratchdir, 'etc/confluentimg.buildinfo')) as imginfo:
for line in imginfo.readlines():
if line.startswith('ARCH='):
imgarch = line.split('=', 1)[1].strip()
except IOError:
pass
if imgarch and imgarch != os.uname().machine:
check_binfmt(imgarch, args)
exitcode = run_constrained(exec_root_backend, args)
if exitcode:
sys.exit(exitcode)
@@ -1077,6 +1116,7 @@ def build_root_backend(optargs):
mkdirp(os.path.join(installroot, 'etc/'))
with open(os.path.join(installroot, 'etc/confluentimg.buildinfo'), 'w') as imginfo:
imginfo.write('BUILDDATE={}\n'.format(datetime.datetime.now().strftime('%Y-%m-%dT%H:%M')))
imginfo.write('ARCH={}\n'.format(oshandler.arch))
if args.source:
imginfo.write('BUILDSRC={}\n'.format(args.source))
@@ -1117,6 +1157,81 @@ def check_root(installroot):
mkdirp(installroot)
qemu_arch_map = {
'aarch64': 'qemu-aarch64',
'x86_64': 'qemu-x86_64',
}
def check_binfmt(targetarch, args):
qname = qemu_arch_map.get(targetarch, 'qemu-' + targetarch)
binfmtdir = '/proc/sys/fs/binfmt_misc'
hostdeb = fingerprint_host_deb(args)
if hostdeb:
# as of ubuntu 26.04, qemu-user-static is a virtual package and the
# statically linked emulators come from qemu-user-binfmt instead
qpkg = 'qemu-user-static'
if float(hostdeb.version) >= 26.04:
qpkg = 'qemu-user-binfmt'
setupmsg = (
'Emulating {0} requires the {2} package, which '
'registers {1} in binfmt_misc with the F (fix-binary) flag '
'("apt-get install {2}", then "update-binfmts '
'--enable {1}" if the handler is disabled)\n'.format(
targetarch, qname, qpkg))
elif fingerprint_host_el(args):
setupmsg = (
'Emulating {0} requires /usr/bin/qemu-{0}-static registered in '
'/etc/binfmt.d/qemu-{0}.conf with the F (fix-binary) flag, '
'followed by "systemctl restart systemd-binfmt"\n'.format(
targetarch))
else:
sys.stderr.write(
'Cross-architecture builds are only supported on EL and Ubuntu '
'build hosts\n')
sys.exit(1)
try:
with open(os.path.join(binfmtdir, 'status')) as statusin:
enabled = statusin.read().strip() == 'enabled'
except IOError:
enabled = False
if not enabled:
sys.stderr.write(
'binfmt_misc is not enabled on this system. ' + setupmsg)
sys.exit(1)
for entry in glob.glob(os.path.join(binfmtdir, '*')):
entryname = os.path.basename(entry)
if entryname in ('register', 'status'):
continue
try:
with open(entry) as entryin:
entryinfo = entryin.read().split('\n')
except IOError:
continue
interpreter = ''
flags = ''
for line in entryinfo[1:]:
if line.startswith('interpreter '):
interpreter = line.split(' ', 1)[1]
elif line.startswith('flags:'):
flags = line.split(':', 1)[1].strip()
if entryname != qname and qname not in interpreter:
continue
if entryinfo[0].strip() != 'enabled':
continue
if 'F' not in flags:
sys.stderr.write(
'binfmt_misc handler {0} lacks the F (fix-binary) flag, so '
'the emulator would not be reachable from within the image '
'chroot. '.format(entryname) + setupmsg)
sys.exit(1)
return
sys.stderr.write(
'No enabled binfmt_misc handler for {0} found. '.format(targetarch)
+ setupmsg)
sys.exit(1)
def fingerprint_source_suse(files, sourcepath, args):
if os.path.exists(os.path.join(sourcepath, 'distinfo.yaml')):
with open(os.path.join(sourcepath, 'distinfo.yaml'), 'r') as distinfo:
@@ -1293,6 +1408,22 @@ def build_root(args):
sys.stderr.write(
'Unable to recognize build system os\n')
sys.exit(1)
hostarch = os.uname().machine
if args.arch and args.arch != oshandler.arch:
if args.source:
sys.stderr.write(
'Requested architecture {0} conflicts with source directory '
'architecture {1}\n'.format(args.arch, oshandler.arch))
sys.exit(1)
oshandler.set_arch(args.arch)
if oshandler.arch != hostarch:
if not oshandler.crossbuild:
sys.stderr.write(
'Building {0} images on a {1} host is currently not '
'supported on this distribution\n'.format(
oshandler.arch, hostarch))
sys.exit(1)
check_binfmt(oshandler.arch, args)
if args.non_interactive:
oshandler.set_interactive(False)
oshandler.set_target(args.scratchdir)
@@ -1425,12 +1556,15 @@ async def pack_image(args):
sys.exit(1)
imginfofile = os.path.join(args.scratchdir, 'etc/confluentimg.buildinfo')
distpath = None
imgarch = None
try:
with open(imginfofile) as imginfoin:
imginfo = imginfoin.read().split('\n')
for lineinfo in imginfo:
if lineinfo.startswith('BUILDSRC='):
distpath = lineinfo.replace('BUILDSRC=', '')
elif lineinfo.startswith('ARCH='):
imgarch = lineinfo.replace('ARCH=', '')
except IOError:
pass
kerns = glob.glob(os.path.join(args.scratchdir, 'boot/vmlinuz-*'))
@@ -1502,12 +1636,24 @@ async def pack_image(args):
profiley.write('label: {0}\nkernelargs: quiet # confluent_imagemethod=untethered|tethered # tethered is default when unspecified to save on memory, untethered will use more ram, but will not have any ongoing runtime root fs dependency on the http servers.\n'.format(label))
oscat = oshandler.oscategory
confdir = '/opt/confluent/lib/osdeploy/{}-diskless'.format(oscat)
archaddon = '/opt/confluent/lib/osdeploy/{}-diskless/initramfs/{}/addons.cpio'.format(oscat, platform.machine())
packarch = imgarch if imgarch else os.uname().machine
archaddon = '/opt/confluent/lib/osdeploy/{}-diskless/initramfs/{}/addons.cpio'.format(oscat, packarch)
addonlink = os.path.join(outdir, 'boot/initramfs/addons.cpio')
if os.path.exists(archaddon):
os.symlink(archaddon, os.path.join(outdir, 'boot/initramfs/addons.cpio'))
else:
os.symlink(archaddon, addonlink)
elif packarch == 'x86_64':
# the unsuffixed addons path carries the x86_64 payload
os.symlink('{}/initramfs/addons.cpio'.format(confdir),
os.path.join(outdir, 'boot/initramfs/addons.cpio'))
addonlink)
else:
# addons of another architecture would contain foreign
# binaries that break boot, so link to the (currently
# missing) target arch path rather than falling back
sys.stderr.write(
'Warning: {0} does not exist, the profile will not be '
'bootable until the confluent_osdeploy-{1} package is '
'installed\n'.format(archaddon, packarch))
os.symlink(archaddon, addonlink)
indir = '{}/profiles/default'.format(confdir)
if os.path.exists(indir):
copy_tree(indir, outdir)