首先，我对 ubuntu 或 linux 不是很熟悉。所以今天我的笔记本电脑无法启动 ubuntu。启动后，它只显示黑屏或联想启动徽标。我也无法进入 grub 菜单，按住 shift 不起作用。我目前正在使用安装棒上的试用版。我运行了启动修复，但它没有给我任何修复选项。
我尝试使用 fdisk，但不知道该怎么用它。这是 fdisk -l 的输出：（Cruzer Blade 是 USB 棒）
Disk /dev/loop0: 2.06 GiB, 2213470208 bytes, 4323184 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/loop1: 55.45 MiB, 58142720 bytes, 113560 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/loop2: 51.04 MiB, 53522432 bytes, 104536 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/loop3: 64.77 MiB, 67915776 bytes, 132648 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/loop4: 218.99 MiB, 229629952 bytes, 448496 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/loop5: 32.27 MiB, 33841152 bytes, 66096 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/sda: 14.32 GiB, 15376318464 bytes, 30031872 sectors
Disk model: Cruzer Blade
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: AF8737A9-1E23-4373-B87A-C8B16199D461
Device Start End Sectors Size Type
/dev/sda1 64 5494643 5494580 2.6G Microsoft basic data
/dev/sda2 5494644 5504683 10040 4.9M EFI System
/dev/sda3 5504684 5505283 600 300K Microsoft basic data
/dev/sda4 5509120 30031808 24522689 11.7G Linux filesystem
我不知道该怎么做才能让 Ubuntu 开始工作。我非常感谢任何帮助！谢谢。