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I have a Samsung RF511 laptop and a new USB 3 2TB external hard drive (Samsung M3 2TB USB 3.0 Portable). The laptop runs Windows 10 so I thought I'd try taking advantage of USB 3's speed to install Ubuntu on the external hard drive. I downloaded 15.10, put it on a USB 2 Pen Drive and followed this answer to install Ubuntu onto the external hard drive.Everything installed fine. I created a 120GB partition for /, a 4GB partition for swap and left the rest for Windows. The MBR was written to the external hard drive.

ubuntu@ubuntu:~$ mount | grep "^/"
/dev/sdc1 on /cdrom type vfat (ro,noatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)
/dev/loop0 on /rofs type squashfs (ro,noatime)
/cow on / type overlay (rw,relatime,lowerdir=//filesystem.squashfs,upperdir=/cow/upper,workdir=/cow/work)
/dev/sdb1 on /media/ubuntu/e9da06b1-bcd9-49ae-9d6d-161b7b70b182 type ext4 (rw,nosuid,nodev,relatime,data=ordered,uhelper=udisks2)
/dev/sdb2 on /media/ubuntu/DATA type fuseblk (rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096,uhelper=udisks2)

ubuntu@ubuntu:~$ ls /cdrom/ # this is the USB2 pen drive
boot    EFI       license.txt  pool                System Volume Information      uui
casper  install   md5sum.txt   preseed             Uni-USB-Installer-Copying.txt
dists   isolinux  pics         README.diskdefines  Uni-USB-Installer-Readme.txt

ubuntu@ubuntu:~$ sudo file -s /dev/sdb # this is the external hard drive
/dev/sdb: DOS/MBR boot sector

ubuntu@ubuntu:~$ ls /media/ubuntu/e9da06b1-bcd9-49ae-9d6d-161b7b70b182/
bin   cdrom  etc   initrd.img  lib64       media  opt   root  sbin  sys  usr  vmlinuz
boot  dev    home  lib         lost+found  mnt    proc  run   srv   tmp  var

However, my laptop doesn't appear to like booting from the external USB 3 hard drive or its USB 3 ports. The USB 2 Pen Drive boots from one of the USB 2 ports, but that's about it. I couldn't even get the external hard drive to boot when connected to the very same USB 2 port.

If I plug the external hard drive into one of the USB 3 slots, the laptop doesn't recognize it as bootable and boots Windows 10 instead.

I was wondering if I could boot from USB 2 using a pen drive, mount the external hard drive using USB 3, and somehow convince grub to boot from /dev/sdb1. Is this possible? Or perhaps any other solution?

  • It looks like you may have installed in BIOS boot mode. You would have to be sure to install grub to MBR of external drive, sdb or sdc or whatever. Or partition in advance using gpt, include ESP - efi system partition and install in UEFI boot mode. But you then need to copy files from sda's ESP to drive's ESP. To see details: help.ubuntu.com/community/Boot-Info and: askubuntu.com/questions/591193/… external drives only boot from /EFI/Boot/bootx64.efi. So some other copies are required. Post preference. – oldfred Feb 24 '16 at 21:57
  • I did install the MBR to sdb. This laptop doesn't have UEFI boot mode, it's a Windows 7-era laptop. – sigint Feb 24 '16 at 22:03
  • Post link to Boot-Repair's Summary Report. Also if Windows 10 and hibernation was on, grub would not have been able to see it to add it to menu. Then you may have to hold shift key to get menu. And depending on if booting with Intel or nVidia may need nomodeset. – oldfred Feb 24 '16 at 23:12

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