Distro Linux Mint 19-3 Tricia
I loaded a 2nd copy of Mint 19-3 onto an external HDD. When done, I failed to remove that external HDD and tried re-booting my laptop .. twice it tried booting the external HDD unsuccessfully.
I removed the external HDD and when rebooting received only a menu allowing me to see what limited commands were available with “grub”.
I used MX-Live (Source-Forge’s Boot-Repair-Disk.iso via usb-stick) and chose “Search Grub Menus” and then got another list where I chose “Load grub menu @(hd3,2)”.
My machine then loaded correctly from the internal HDD but now, I have to go THROUGH MX-Live for every bootup. How can I repair my machine’s boot?

Current /boot is.......
------------------------------------------------------------------------------
root@HPLap:/boot# ls
config-5.0.0-32-generic memtest86+.elf
config-5.4.0-39-generic memtest86+_multiboot.bin
config-5.4.0-40-generic System.map-5.0.0-32-generic
efi System.map-5.4.0-39-generic
grub System.map-5.4.0-40-generic
initrd.img-5.0.0-32-generic vmlinuz-5.0.0-32-generic
initrd.img-5.4.0-39-generic vmlinuz-5.4.0-39-generic
initrd.img-5.4.0-40-generic vmlinuz-5.4.0-40-generic
memtest86+.bin
-------------------------------------------------------------------------------

Current lsblk......
-------------------------------------------------------------------
root@HPLap:/boot# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 465.8G 0 disk
├─sda1 8:1 0 512M 0 part /boot/efi
└─sda2 8:2 0 465.3G 0 part /
sdb 8:16 1 31.3G 0 disk
├─sdb1 8:17 1 1.5G 0 part /media/garyh/MX-Live
└─sdb2 8:18 1 3.1M 0 part
sdc 8:32 1 500G 0 disk
└─sdc1 8:33 1 500G 0 part /media/garyh/BLU500G
sdd 8:48 1 29.7G 0 disk
└─sdd1 8:49 1 29.7G 0 part /media/garyh/MICRO32G
sde 8:64 0 698.7G 0 disk
└─sde1 8:65 0 698.7G 0 part /mnt/wwn-0x50014ee658b790be-part1
sr0 11:0 1 1024M 0 rom
-----------------------------------------------------------------------------

Current parted --list ......
-----------------------------------------------------------------------------
Model: ATA WDC WD5000LPCX-6 (scsi)
Disk /dev/sda: 500GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Disk Flags:

Number Start End Size File system Name Flags
1 1049kB 538MB 537MB fat32 EFI System Partition boot, esp
2 538MB 500GB 500GB ext4


Model: General UDisk (scsi)
Disk /dev/sdb: 33.6GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number Start End Size Type File system Flags
2 596kB 3881kB 3285kB primary esp


Model: USB 2.0 PenDrive (scsi)
Disk /dev/sdc: 537GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number Start End Size Type File system Flags
1 1049kB 537GB 537GB primary


Model: Generic- SD/MMC/MS PRO (scsi)
Disk /dev/sdd: 31.9GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number Start End Size Type File system Flags
1 1049kB 31.9GB 31.9GB primary fat32 lba


Model: Generic External (scsi)
Disk /dev/sde: 750GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number Start End Size Type File system Flags
1 1049kB 750GB 750GB primary ext4

----------------------------------------------------------------------------------------

Rerun sudo grub-install, after booting into the mint on your internal drive

Thank you! SOLVED.
I didn't search far enough for just such a simple answer.

your welcome