下列的Ubuntu Touch 官方安装说明我总是卡在引导加载程序“下载......”中，而终端显示：
mizz@Miz:~$ ubuntu-device-flash touch --channel=ubuntu-touch/stable/ubuntu --bootstrap
2016/11/23 11:04:44 Expecting the device to be in the bootloader... waiting
2016/11/23 11:04:44 Device is |mako|
2016/11/23 11:04:45 Flashing version 33 from ubuntu-touch/stable/ubuntu channel and server https://system-image.ubuntu.com to device mako
22.61 MB / 22.61 MB [===] 100.00 % 1.28 MB/s
52.70 MB / 52.70 MB [===] 100.00 % 1.99 MB/s
298.13 MB / 298.13 MB [===] 100.00 % 4.39 MB/s
（其他时候只是没有最后三行。）
关闭手机并重新打开后，一切（启动+恢复+AndroidOS）均恢复正常。
或者，按照双启动安装说明当终端显示时，我也陷入引导加载程序“下载......”中：
mizz@Miz:~$ ./dualboot.sh
No device ID specified, picking first available device
Waiting for device 016fd3888d0d4647 to install Ubuntu installer to.
Detected connected Nexus 4
Downloading recovery for mako
ls: cannot access 'recovery-mako-6.0.4.3.img': No such file or directory
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 8400k 100 8400k 0 0 2735k 0 0:00:03 0:00:03 --:--:-- 2735k
Downloaded file has size: 8601600
Dafaulting to auto action
Device 016fd3888d0d4647 bin: , xbin: , CM_DEVICE: mako
selecting UPDATE mode
Downloading Ubuntu Installer application package
ls: cannot access 'UPDATE-UbuntuInstaller.zip': No such file or directory
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 2266k 100 2266k 0 0 418k 0 0:00:05 0:00:05 --:--:-- 467k
Downloaded file has size: 2321175
install_ubuntu_installer<<
Dev:016fd3888d0d4647: Rebooting to bootloader
Waiting for device to be connected in normal or recovery mode
Dev:016fd3888d0d4647: Waiting for fastboot to be ready
downloading 'boot.img'...
再次关闭手机并重新打开后，一切恢复正常。
请问您知道我为什么会被困在那里吗？
PS Cyanogenmod 13 安装了 CM SuperUser 和新的 TWRP，允许 USB 调试，引导加载程序解锁，设备上有超过 3GB 的可用空间。
编辑：之后我使用 Google Play 中的 MultiROM Manager 应用程序以双启动模式安装 Ubuntu Touch，现在两个操作系统都运行正常。