Request to repair the error of qemu nbd in the switch_root process about dracut HOT 5 OPEN

There is also a systemd issue - systemd/systemd#31690 that you did not linked to

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Who knows how to protect specific processes during switch switching
https://mirrors.edge.kernel.org/pub/linux/utils/boot/dracut/dracut.html#_cleanup_and_switch_root

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hCorrelation of similar problems
#1032

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This is some of my handling, although not successful. However, some information can be provided to facilitate understanding
{
echo "[Unit]"
echo "Before=initrd-root-fs.target"
echo "[Mount]"
echo "Where=/sysroot"
echo "What=/dev/nbd0p2"
echo "Type=ext4"
echo "Options=rw"
} > /etc/systemd/system/sysroot.mount

            {            
            echo  "[Unit]"
            echo  "Description=Qemu NBD Server"
            echo  "After=network.target"
            echo  "[Service]"
            echo  "ExecStart=qemu-nbd -c  /dev/nbd0  /host$QEMUNBD"
            echo  "Restart=always"
            echo  "RootService=true"
            echo  "SurviveFinalKillSignal=yes"
            echo  "[Install]"
            echo  "WantedBy=multi-user.target"
            }    > /etc/systemd/system/qemu-nbd.service

Reference:
https://systemd.io/ROOT_STORAGE_DAEMONS/

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logs：
[ 24.890490] fedora systemctl[976]: Bus n/a: changing state UNSET → OPENING
[ 24.890784] fedora systemctl[976]: sd-bus: starting bus by connecting to /run/systemd/private...
[ 24.891276] fedora systemctl[976]: Bus n/a: changing state OPENING → AUTHENTICATING
[ 24.891560] fedora systemctl[976]: Executing dbus call org.freedesktop.systemd1.Manager StartUnit(initrd-switch-root.target, isolate)
[ 24.893117] fedora systemctl[976]: Bus n/a: changing state AUTHENTICATING → RUNNING
[ 24.893464] fedora systemctl[976]: Sent message type=method_call sender=n/a destination=org.freedesktop.systemd1 path=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=StartUnit cookie=1 reply_cookie=0 signature=ss error-name=n/a error-message=n/a
[ 24.894369] fedora systemctl[976]: Got message type=method_return sender=org.freedesktop.systemd1 destination=n/a path=n/a interface=n/a member=n/a cookie=3 reply_cookie=1 signature=o error-name=n/a error-message=n/a
[ 24.894893] fedora systemctl[976]: Sent message type=method_call sender=n/a destination=org.freedesktop.systemd1 path=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=GetUnit cookie=2 reply_cookie=0 signature=s error-name=n/a error-message=n/a
[ 24.896499] fedora systemctl[976]: Got message type=method_return sender=org.freedesktop.systemd1 destination=n/a path=n/a interface=n/a member=n/a cookie=114 reply_cookie=2 signature=o error-name=n/a error-message=n/a
[ 24.898173] fedora systemctl[976]: Sent message type=method_call sender=n/a destination=org.freedesktop.systemd1 path=/org/freedesktop/systemd1/unit/initrd_2dswitch_2droot_2etarget interface=org.freedesktop.DBus.Properties member=Get cookie=3 reply_cookie=0 signature=ss error-name=n/a error-message=n/a
[ 24.955170] fedora systemctl[976]: Got message type=method_return sender=org.freedesktop.systemd1 destination=n/a path=n/a interface=n/a member=n/a cookie=288 reply_cookie=3 signature=v error-name=n/a error-message=n/a
[ 24.955987] fedora systemctl[976]: Bus n/a: changing state RUNNING → CLOSED
[ 25.003636] fedora systemd-journald[393]: Successfully sent stream file descriptor to service manager.
[ 25.001777] fedora udevadm[979]: Found cgroup2 on /sys/fs/cgroup/, full unified hierarchy
[ 25.001777] fedora udevadm[979]: Found container virtualization none.
[ 25.009743] fedora udevadm[979]: SELinux enabled state cached to: disabled
[ 25.034886] fedora systemd-journald[393]: Successfully sent stream file descriptor to service manager.
[ 25.041328] fedora @ystemctl[981]: Bus n/a: changing state UNSET → OPENING
[ 25.042086] fedora @ystemctl[981]: sd-bus: starting bus by connecting to /run/systemd/private...
[ 25.042595] fedora @ystemctl[981]: Bus n/a: changing state OPENING → AUTHENTICATING
[ 25.042985] fedora @ystemctl[981]: Switching root - root: /sysroot; init: n/a
[ 25.044560] fedora @ystemctl[981]: Bus n/a: changing state AUTHENTICATING → RUNNING
[ 25.045388] fedora @ystemctl[981]: Sent message type=method_call sender=n/a destination=org.freedesktop.systemd1 path=/org/freedesktop/systemd1 interface=org.freedesktop.systemd1.Manager member=SwitchRoot cookie=1 reply_cookie=0 signature=ss error-name=n/a error-message=n/a
[ 25.055008] fedora @ystemctl[981]: Got message type=method_return sender=org.freedesktop.systemd1 destination=n/a path=n/a interface=n/a member=n/a cookie=1 reply_cookie=1 signature=n/a error-name=n/a error-message=n/a
[ 25.056204] fedora @ystemctl[981]: Bus n/a: changing state RUNNING → CLOSED
[ 25.182251] fedora kernel: block nbd0: shutting down sockets

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