我错误地删除了 mbr。
现在无法启动ubuntu，所以想重新安装grub。
我正在跟进这指示。
问题是我收到了这个错误：
grub-install --boot-directory=/media/cab64688-2d97-4bbd-9f32-7bc0badb40a8/boot /dev/sdb
rm: cannot remove `/media/cab64688-2d97-4bbd-9f32-7bc0badb40a8/boot/grub/915resolution.mod': Read-only file system
因此，问题是我现有的 ubuntu 分区是只读安装的。当我尝试：
sudo mount /dev/sdb7 /media/ubuntu_mpt
mount: block device /dev/sdb7 is write-protected, mounting read-only
由于我处于只读模式，因此我无法安装 grub。
任何想法？
提前致谢。
编辑：在 apt-get install grub 之后，我重复了该过程并得到：
Probing devices to guess BIOS drives. This may take a long time.
Unknown partition table signature
sed: can't read /media/cab64688-2d97-4bbd-9f32-7bc0badb40a8_/boot/grub/device.map: No such file or directory
grep: /media/cab64688-2d97-4bbd-9f32-7bc0badb40a8_/boot/grub/device.map: No such file or directory
/dev/sda does not have any corresponding BIOS drive.
编辑：要求的输出：
fdisk -l
Disk /dev/sda: 163.9 GB, 163927522816 bytes
255 heads, 63 sectors/track, 19929 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sda doesn't contain a valid partition table
Disk /dev/sdb: 640.1 GB, 640133946880 bytes
255 heads, 63 sectors/track, 77825 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x3dcf5202
Device Boot Start End Blocks Id System
/dev/sdb1 * 1 3917 31463271 7 HPFS/NTFS
/dev/sdb2 3918 77826 593667163 f W95 Ext'd (LBA)
/dev/sdb5 3918 43080 314576766 7 HPFS/NTFS
/dev/sdb6 77328 77826 4000768 82 Linux swap / Solaris
/dev/sdb7 43081 77197 274041856 83 Linux
/dev/sdb8 77197 77327 1045504 82 Linux swap / Solaris
Partition table entries are not in disk order
Disk /dev/sdc: 4043 MB, 4043284480 bytes
125 heads, 62 sectors/track, 1018 cylinders
Units = cylinders of 7750 * 512 = 3968000 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x6f20736b
This doesn't look like a partition table
Probably you selected the wrong device.
Device Boot Start End Blocks Id System
/dev/sdc1 ? 100405 247697 570754815+ 72 Unknown
Partition 1 has different physical/logical beginnings (non-Linux?):
phys=(357, 116, 40) logical=(100404, 79, 11)
Partition 1 has different physical/logical endings:
phys=(357, 32, 45) logical=(247696, 24, 51)
Partition 1 does not end on cylinder boundary.
/dev/sdc2 ? 21767 271577 968014120 65 Novell Netware 386
Partition 2 has different physical/logical beginnings (non-Linux?):
phys=(288, 115, 43) logical=(21766, 48, 47)
Partition 2 has different physical/logical endings:
phys=(367, 114, 50) logical=(271576, 60, 42)
Partition 2 does not end on cylinder boundary.
/dev/sdc3 ? 241276 491086 968014096 79 Unknown
Partition 3 has different physical/logical beginnings (non-Linux?):
phys=(366, 32, 33) logical=(241275, 3, 30)
Partition 3 has different physical/logical endings:
phys=(357, 32, 43) logical=(491085, 14, 39)
Partition 3 does not end on cylinder boundary.
/dev/sdc4 ? 372346 372354 27749+ d Unknown
Partition 4 has different physical/logical beginnings (non-Linux?):
phys=(372, 97, 50) logical=(372345, 119, 25)
Partition 4 has different physical/logical endings:
phys=(0, 10, 0) logical=(372353, 14, 33)
Partition 4 does not end on cylinder boundary.
Partition table entries are not in disk order
mount
aufs on / type aufs (rw)
none on /proc type proc (rw,noexec,nosuid,nodev)
none on /sys type sysfs (rw,noexec,nosuid,nodev)
fusectl on /sys/fs/fuse/connections type fusectl (rw)
none on /dev type devtmpfs (rw,mode=0755)
none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
/dev/sr0 on /cdrom type iso9660 (ro,noatime)
/dev/loop0 on /rofs type squashfs (ro,noatime)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
none on /dev/shm type tmpfs (rw,nosuid,nodev)
tmpfs on /tmp type tmpfs (rw,nosuid,nodev)
none on /var/run type tmpfs (rw,nosuid,mode=0755)
none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
gvfs-fuse-daemon on /home/ubuntu/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=ubuntu)
/dev/sda on /media/Backup type ext4 (rw,nosuid,nodev,uhelper=udisks)
/dev/sdb7 on /media/cab64688-2d97-4bbd-9f32-7bc0badb40a8_ type ext4 (ro,nosuid,nodev,uhelper=udisks)
ls -lA /dev/disk/by-label
total 0
lrwxrwxrwx 1 root root 9 2011-06-12 18:32 Backup -> ../../sda
lrwxrwxrwx 1 root root 9 2011-06-12 18:31 Ubuntu\x2011.04\x20i386 -> ../../sr0
答案1
只需插入 live cd 并使用 livecd 启动 ubuntu。然后转到
应用程序->附件->终端，然后输入 sudo fdisk -l 并找到 ubuntu 安装的分区。
然后在终端中输入以下内容
sudo mkdir /media/sdax （这里 x 是 ubuntu 安装的分区号）
sudo mount /dev/sdax /media/sdax
sudo grub-install --root-directory=/media/sdax /dev/sda
然后重新启动系统（不使用 Live CD），并在终端中输入以下内容
sudo 更新 grub
答案2
我在以下帮助下解决了这个问题联合国网启动。安装后成功启动我的 ubuntu 系统（cnosole 模式或较差的图形模式）。无论从这两个启动哪个，只需运行 grub-install /dev/sdb，其中 /dev/sdb 是 bios 中设置的启动硬盘。重新启动，grub 应该可以正常工作。
答案3
使用如下命令-->
sudo mount /dev/ROOT_PARTITION /opt
sudo grub-install --root-directory=/opt /dev/sda
答案4
我刚刚遇到了一个类似的问题，而我手头只有一个 Ubuntu 14.04“迷你”启动盘 - 所以这就是我的做法：
- 从迷你启动盘启动并在高级选项中选择“救援模式”（实际上选择哪个可能并不重要）
- 当安装程序启动时，选择“返回”以获取主菜单。
- 选择“启动 shell”。老实说，任何能提供 shell 的 Linux 启动盘都可以帮你完成这一步。
- 挂载 linux 分区
- 将 /dev、/proc 和 /sys 绑定挂载到已挂载分区
- Chroot 到该分区
- 从 chroot 运行 grub-install 和 update-grub2（mini 没有安装 grub 工具）。
# mount /dev/sda5 /mnt # mount -o bind /dev /mnt/dev # mount -o bind /proc /mnt/proc # mount -o bind /sys /mnt/sys # chroot /mnt /bin/bash ~# grub-install --root-directory=/ /dev/sda ~# update-grub2 ~# ^D # reboot
瞧 — — grub 回来了。
（此网站上的代码缩进不起作用……？）