Challenges in installing Linux Mint 19 to dual boot along side windows

 WARNING: There is an updated Install notes. Check out  the recent post
Had a tough time setting/installing up Linux mint 19 on my existing dual boot machine to solve these 2 problems:
1. grub-efi-amd64-signed' package failed to install into /target
2. Hash Sum mismatch.
3. shim-signed and grub-efi-amd64-signed failure to configure.
Huh. Nearly 6 hours trying to figure out. #Linuxmint

As it happened:

I had a Linux mint 18 and a rusted windows. So I wanted to refresh my machine. So I reset factory/recovery settings on windows. And wished to install Linux mint afresh. So, I have downloaded the ISO file named linuxmint-19-cinnamon-64bit-v2.iso from the official website and verified. I have made necessary partitions while installing and installation went smooth. However, right after installing and just before grub installation, this error came up.

"GRUB Installation Failed.
The 'grub-efi-amd64-signed' package failed to install into /target/. Without the GRUB boot loader, the installed system will not boot".


To rectify this.
1. install boot-repair

sudo add-apt-repository ppa:yannubuntu/boot-repair
sudo apt-get update

sudo apt-get install boot-repair 

Open boot repair and run the recommended things. [it took 20mins; be patient] It will FAIL badly. Never mind go ahead and restart it. It worked. Because it has successfully reinstalled grub.

2. apt-get update would not completed it will show error like "Hash Sum mismatch"

E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/bionic-updates/main/binary-i386/by-hash/SHA256/a70a891ed73362c0a3966c9c6c790096f5aba663389ab578a6b991b698ae43c6  Hash Sum mismatch
   Hashes of expected file:
    - Filesize:393124 [weak]
    - SHA256:a70a891ed73362c0a3966c9c6c790096f5aba663389ab578a6b991b698ae43c6
    - SHA1:4e0cfabaaf47b0cbf6ecc284e5281430bbe530d2 [weak]
    - MD5Sum:94742010fa630d152bbff1445f6369b4 [weak]
   Hashes of received file:
    - SHA256:ea9bf28ed7d57e5bd739fc63485459130475026c35a84f25e57d2f5ca0521ec7
    - SHA1:af7bad4e086d5e768c450c77032ee520d58afeda [weak]
    - MD5Sum:aa28e356c8a66b4838a83ab18e10e2d5 [weak]
    - Filesize:393124 [weak]
   Last modification reported: Fri, 23 Nov 2018 12:50:34 +0000
   Release file created at: Fri, 23 Nov 2018 13:51:10 +0000

To resolve this:

sudo apt-get clean

sudo rm -rf /var/lib/apt/lists/partial

sudo apt-get update -o Acquire::CompressionTypes::Order::=gz

sudo apt-get update

Resolve steps 2:
I am not sure above steps did resolve it completely. because I was still getting. Hash sum mismatch even after doing that.

Changing the main mirrors to different URL in Software source actually fixed in.

3. New problems:
Everytime I installed some pkg
It would try install some failed installed packages such as
shim-signed
grub-efi-amd64-signed

Resolve steps

sudo rm /sys/firmware/efi/efivars/dump-*
sudo update-grub
sudo apt-get -f install
References

Linux mint and askubuntu forums.