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osbuilder: Include minimal set of device nodes in ubuntu initrd

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When starting an initrd the kernel expects to find /dev/console in the initrd,
so that it can connect it as stdin/stdout/stderr to the /init process. If the
device node is missing the kernel will complain that it was unable to open an
initial console. If kata-agent is the initrd init process, it will also result
in log messages not being logged to console and thus not forwarded to host
syslog.

Add a set of standard device nodes for completeness, so that console logging
works. To do that we install the makedev packge which provides a MAKEDEV helper
that knows the major/minor numbers. Unfortunately the debian package tries to
create devnodes from postinst, which can be suppressed if systemd-detect-virt
is present. That's why we create a small dummy script that matches what
systemd-detect-virt would output (anything is enough to suppress mknod).

Fixes: #6261
Signed-off-by: Jeremi Piotrowski <jpiotrowski@microsoft.com>
This commit is contained in:
Jeremi Piotrowski 2023-02-10 11:43:31 +01:00
parent 86501d5f6f
commit 76e926453a
2 changed files with 9 additions and 0 deletions
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3
tools/osbuilder/rootfs-builder/ubuntu/Dockerfile.in
View File

@ -6,6 +6,8 @@ ARG IMAGE_REGISTRY=docker.io
FROM ${IMAGE_REGISTRY}/ubuntu:@OS_VERSION@
@SET_PROXY@
# makedev tries to mknod from postinst
RUN [ -x /usr/bin/systemd-detect-virt ] || ( echo "echo docker" >/usr/bin/systemd-detect-virt && chmod +x /usr/bin/systemd-detect-virt )
RUN apt-get update && \
DEBIAN_FRONTEND=noninteractive \
apt-get --no-install-recommends -y install \
@ -20,6 +22,7 @@ RUN apt-get update && \
echo "gcc-$gcc_arch-linux-gnu libc6-dev-$libc_arch-cross")) \
git \
make \
makedev \
multistrap \
musl-tools \
protobuf-compiler

6
tools/osbuilder/rootfs-builder/ubuntu/rootfs_lib.sh
View File

@ -34,4 +34,10 @@ EOF
# Reduce image size and memory footprint by removing unnecessary files and directories.
rm -rf $rootfs_dir/usr/share/{bash-completion,bug,doc,info,lintian,locale,man,menu,misc,pixmaps,terminfo,zsh}
# Minimal set of device nodes needed when AGENT_INIT=yes so that the
# kernel can properly setup stdout/stdin/stderr for us
pushd $rootfs_dir/dev
MAKEDEV -v console tty ttyS null zero fd
popd
}