通过复制系统文件安装的Ubuntu无法启动

我试图通过在从 LiveCD 运行时复制所有文件来将现有的 Ubuntu 安装移动到新分区。最后，新系统卡在启动过程中。

我做了什么

1. 启动的 LiveCD。
2. 挂载新旧分区。
3. 使用类似cp -a /mnt/old_root/* /mnt/new_root复制文件的方法，据说可以保留文件元数据。（也许我应该尝试其他选择）
4. /etc/fstab在新系统上更正。
5. 按照第一次尝试中的这些步骤和第二次尝试中的这些步骤重新安装 GRUB 。
6. 尝试启动新系统。
7. 修复了这个问题，但这不是原因。

UPD：我尝试在新安装的系统上执行相同的步骤并得到相同的结果。

不重要的细节：

1. 我在 VirtualBox 版本 6.0.5 r128870 中运行系统
2. 系统为Ubuntu 18.04.2 LTS；Linux 4.15.0-45 通用。

我得到了什么

• 系统启动开始。
• 看起来系统成功挂载/并且/home. （当系统出现错误时/etc/fstab迅速掉线到维修shell）
• 系统启动卡在动画闪屏中。
• 如果我隐藏启动画面，我会看到相同的服务一遍又一遍地无法启动。该系统几乎不使用 CPU 或存储。
• 我可以从 GRUB 启动到恢复模式。
• 日志中的第一条错误消息：

2019-02-19T18:29:37+0000 hostname systemd[1]: Reached target Sockets.
2019-02-19T18:29:37+0000 hostname systemd[1]: Reached target Basic System.
2019-02-19T18:29:37+0000 hostname systemd[1]: Started D-Bus System Message Bus.
2019-02-19T18:29:37+0000 hostname dbus-daemon[1104]: dbus[1104]: Unknown group "power" in message bus configuration file
2019-02-19T18:31:07+0000 hostname systemd[1]: Failed to get initial list of names: Connection timed out
2019-02-19T18:31:07+0000 hostname systemd[1]: Failed to set up API bus: Connection timed out
2019-02-19T18:31:07+0000 hostname systemd[1]: Error occured during D-Bus APIs initialization: Connection timed out
2019-02-19T18:31:07+0000 hostname systemd[1]: Starting Login Service...
2019-02-19T18:31:07+0000 hostname systemd[1]: Starting System Logging Service...
2019-02-19T18:31:07+0000 hostname systemd[1]: Starting firewalld - dynamic firewall daemon...
2019-02-19T18:31:07+0000 hostname systemd[1]: Starting Detect the available GPUs and deal with any system changes...
2019-02-19T18:31:07+0000 hostname systemd[1]: Starting Avahi mDNS/DNS-SD Stack...
2019-02-19T18:31:07+0000 hostname systemd[1]: Started CUPS Scheduler.
2019-02-19T18:31:07+0000 hostname systemd[1]: Starting LSB: OpenIPMI Driver init script...
2019-02-19T18:31:07+0000 hostname systemd[1]: Starting WPA supplicant...
2019-02-19T18:31:08+0000 hostname avahi-daemon[1138]: Found user 'avahi' (UID 115) and group 'avahi' (GID 122).
2019-02-19T18:31:08+0000 hostname avahi-daemon[1138]: Successfully dropped root privileges.
2019-02-19T18:31:08+0000 hostname avahi-daemon[1138]: open(/run/avahi-daemon//pid): Permission denied
2019-02-19T18:31:08+0000 hostname avahi-daemon[1138]: Failed to create PID file: Permission denied

• 此类消息每 90 秒重复一次。据我了解，dbus-daemon 死了。

2019-02-19T20:53:47+0000 hostname systemd[1]: Failed to get initial list of names: Connection timed out
2019-02-19T20:53:47+0000 hostname systemd[1]: Failed to set up API bus: Connection timed out
2019-02-19T20:53:47+0000 hostname systemd[1]: Error occured during D-Bus APIs initialization: Connection timed out
2019-02-19T20:53:47+0000 hostname systemd[1]: Starting Network Manager...
2019-02-19T20:53:47+0000 hostname systemd[1]: dbus.service: Main process exited, code=exited, status=1/FAILURE
2019-02-19T20:53:47+0000 hostname systemd[1]: dbus.service: Failed with result 'exit-code'.
2019-02-19T20:53:47+0000 hostname systemd[1]: rsyslog.service: Start operation timed out. Terminating.
2019-02-19T20:53:47+0000 hostname systemd[1]: whoopsie.service: Service hold-off time over, scheduling restart.
2019-02-19T20:53:47+0000 hostname systemd[1]: whoopsie.service: Scheduled restart job, restart counter is at 7.
2019-02-19T20:53:47+0000 hostname systemd[1]: Started D-Bus System Message Bus.
2019-02-19T20:53:47+0000 hostname dbus-daemon[4650]: dbus[4650]: Unknown group "power" in message bus configuration file
2019-02-19T20:53:47+0000 hostname NetworkManager[4644]: <info>  [1550609627.2637] NetworkManager (version 1.10.6) is starting... (after a restart)
2019-02-19T20:53:47+0000 hostname NetworkManager[4644]: <info>  [1550609627.2641] Read config: /etc/NetworkManager/NetworkManager.conf (lib: 10-dns-resolved.conf, 20-connectivity-ubuntu.conf, no-mac-addr-change.conf) (run: netplan.conf) (etc: 10-globally-managed-devices.conf, 10-ubuntu-fan.conf, default-wifi-powersave-on.conf)
2019-02-19T20:55:17+0000 hostname systemd[1]: Failed to get initial list of names: Connection timed out
2019-02-19T20:55:17+0000 hostname systemd[1]: Failed to set up API bus: Connection timed out
2019-02-19T20:55:17+0000 hostname systemd[1]: Error occured during D-Bus APIs initialization: Connection timed out
2019-02-19T20:55:17+0000 hostname systemd[1]: Stopped crash report submission daemon.
2019-02-19T20:55:17+0000 hostname systemd[1]: Started crash report submission daemon.
2019-02-19T20:55:17+0000 hostname systemd[1]: rsyslog.service: Main process exited, code=killed, status=6/ABRT
2019-02-19T20:55:17+0000 hostname systemd[1]: rsyslog.service: Failed with result 'timeout'.
2019-02-19T20:55:17+0000 hostname systemd[1]: Failed to start System Logging Service.
2019-02-19T20:55:17+0000 hostname systemd[1]: dbus.service: Main process exited, code=exited, status=1/FAILURE
2019-02-19T20:55:17+0000 hostname systemd[1]: dbus.service: Failed with result 'exit-code'.
2019-02-19T20:55:17+0000 hostname systemd[1]: NetworkManager.service: Start operation timed out. Terminating.
2019-02-19T20:55:17+0000 hostname systemd[1]: Started D-Bus System Message Bus.
2019-02-19T20:55:17+0000 hostname whoopsie[4678]: [20:55:17] Could not create lock directory.
2019-02-19T20:55:17+0000 hostname whoopsie[4678]: [20:55:17] Using lock path: /var/lock/whoopsie/lock
2019-02-19T20:55:17+0000 hostname whoopsie[4678]: [20:55:17] Could not create lock file: Bad file descriptor
2019-02-19T20:55:17+0000 hostname whoopsie[4678]: [20:55:17] Could not read directory (13): /var/crash
2019-02-19T20:55:17+0000 hostname dbus-daemon[4685]: dbus[4685]: Unknown group "power" in message bus configuration file
2019-02-19T20:55:17+0000 hostname snapd[1246]: udevmon.go:190: udev monitor observed remove event for unknown device "/sys/dentry(4893:whoopsie.service)"

问题

1. 当时cp -a预计的工作？
2. 新旧分区的区别在哪里？
3. 我应该深入研究引导问题本身吗？