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9h
comment ubuntu no longer starting in secure mode
The command you specified should work if Shim is on /dev/sdb1. If so, you should see an entry in the efibootmgr -v output pointing to the shimx64.efi binary, and the BootOrder line should show that entry's number first in the list. If you don't see the new entry, then something was wrong with the command; and if you see it but it's not first in BootOrder, you may need to use the -o option to efibootmgr to adjust the boot order. Updating the efibootmgr -v output you added may be helpful at this point.
11h
comment ubuntu no longer starting in secure mode
Please edit your question to show the output of sudo efibootmgr -v. Add four spaces to the start of each line to maintain legibility. Note that the boot numbers (Boot0000, Boot001A, etc.) have nothing to do with the boot order; that is determined by the BootOrder variable. It's possible that your boot order has gotten messed up, so with any luck that may be all you'll need to fix.
14h
answered ubuntu no longer starting in secure mode
15h
comment “Error: Invalid signature” when configuring dual boot Ubuntu 14.04 and Windows 10
In theory, typing sudo efibootmgr -o 0001,0002 should get your system to boot GRUB by default. In practice, some EFIs are broken and this won't work. Sometimes this procedure fixes the problem, but other times you need an ugly hack, as described on this page of mine.
15h
comment How does dd write to a device node when you usually can't?
The whole-disk device views the device as a whole; partitions don't enter into the picture. By definition, a partition is a part of a whole device. Every partition-table format of which I'm aware stores partitioning data on the device, and that partitioning data is outside of the partitions themselves, so it's impossible for a partition to cover the entire device -- at least one sector (and usually more) is excluded from the partitioned space. This is largely a linguistic distinction, though.
1d
answered How does dd write to a device node when you usually can't?
1d
comment Removing Partition in Hard Drive
This procedure assumes a BIOS-mode installation, which is an unsafe assumption. Assessing the boot mode first, by looking for a /sys/firmware/efi directory (present only in EFI-mode boots) and adjusting the procedure accordingly is necessary to make this procedure safe.
1d
comment How to increase /boot partition size when installing Ubuntu 14.04 using the “use entire disk and set up encrypted LVM” option?
AFAIK, it can't be done via that option; you should consider using the "Something Else" option instead, as described here (among many other places). FWIW, this bug report identifies a too-small /boot partition as a problem. If you agree, please click the link that identifies you as being affected, and perhaps add a comment.
1d
answered GParted showing incorrect used space
1d
answered fsck wont fix efs partitions
1d
comment GRUB wont recognize ubuntu
Try running Boot Repair. If that doesn't work, post the URL that Boot Repair presents.
1d
answered “Fixing Grub” in single boot installation process
1d
comment “Error: Invalid signature” when configuring dual boot Ubuntu 14.04 and Windows 10
Sorry, I got confused and thought nothing was booting. If you have no ESP, though, Ubuntu cannot be booting in EFI mode, so you'll need to create an ESP and install an EFI-mode boot loader in it. If you can recover your earlier ESP, then that's the simpler solution.
1d
comment “Error: Invalid signature” when configuring dual boot Ubuntu 14.04 and Windows 10
/dev/sda4 was not your Windows partition; as I stated, it was your ESP -- what Boot Repair calls the "EFI partition." With it gone, so is your Windows boot loader. At this point, you can either try recovering the ESP with gdisk or parted (but do not try to create a filesystem on it or use GParted); or you can back up your personal data, delete all the partitions, and install everything from scratch.
1d
answered “Error: Invalid signature” when configuring dual boot Ubuntu 14.04 and Windows 10
1d
comment Can I create a bootable Windows 7 installation USB from within Ubuntu to boot a 2010 model iMac?
AFAIK all x86-based Macs provide a CSM (and hence BIOS/legacy support). The earliest models require a firmware update to add this support, but I'd expect it would have been present in your 2010 model from the start. This support is typically activated when the firmware notices an MBR (or hybrid MBR) partition table or a CD/DVD with BIOS-mode boot loader. The computer can still boot in EFI mode with the CSM activated; activation of the CSM simply enables a BIOS-mode boot as an option.
2d
comment GRUB 2 dual boot freeze for a few seconds
I've never heard of that problem. You might try another EFI boot manager, at least to see if the problem persists with a different boot manager. Most EFIs provide a built-in boot manager you can access by pressing a function key at boot (which one varies between computers). There are also several other EFI boot loaders and managers for Linux, as noted on this page of mine. Most will require you to disable Secure Boot, but that might be worth it for a test.
2d
comment How can I boot from a USB device via grub shell or initramfs?
Post the URL that Boot Repair gives you. Without that, much more is guesswork.
2d
comment How do you restore bootable flag to windows partition?
EFI is a type of firmware. GPT is a disk partitioning system. Windows boots in EFI mode only from GPT disks. Thus, your statement that "...it boots into efi fine, but not into GPT any longer..." makes little sense, unless perhaps you mean you can access the firmware setup utility but not boot the computer. Based on my answer, I suspect you once had a link to Boot Info Script or Boot Repair output, but that's gone now, so I can't re-review your setup.
2d
comment GParted will not start, corrupt GPT table
See the Fake RAID HOWTO for information on how to use that technology. Depending on your needs (dual boot, etc.) you might want to completely deactivate it and use the two disks separately or activate it fully and use the two disks as if they were one. Personally, I'd avoid this type of RAID on an Ubuntu-only installation.