/etc # cat fstab
cat fstab
/proc /proc proc defaults 0 0
/sys /sys sysfs defaults 0 0
devtmpfs /dev devtmpfs defaults 0 0

I don't thing the / should be at the beginning of proc and sys lines.

Please explain..

Once again, this is a EMMC disk.

your mounting /proc to /proc instead of the proc filesystem /proc
https://man7.org/linux/man-pages/man5/procfs.5.html
I think the next line should begin with sysfs not sys
https://man7.org/linux/man-pages/man5/sysfs.5.html

Here is the content on a similar Control4 EA-1 Controller filesystem.

/etc# cat fstab
/proc /proc proc defaults 0 0
/sys /sys sysfs defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
tmpfs /tmp tmpfs size=32m 0 0
tmpfs /var tmpfs size=64m 0 0
rootfs / ext4 remount,rw,errors=remount-ro,discard,noatime,data=ordered,nobarrier 0 1
/dev/mmcblk0p3 /mnt/persistent ext4 rw,errors=remount-ro,discard,noatime,data=ordered,nobarrier 0 1
cgroup /sys/fs/cgroup cgroup defaults 0 0

I posted the fstab information from a similar Control4 Controller filesystem.

If that works, then I must be wrong. It wouldn't be the first time I was wrong about something and won't be the last. Sorry about that.
It seams to me it is missing some of the other content that is in the other fstab.

Explain what the content in this file does?

Don't get carried away. The problem is corrupted filesystem, and the question is why. If the memory device is failing then the only fix is replacing it. Is it replaceable?

If I wanted to add the following line to the fstab file, how would I do that? Using vi? Please advise.

rootfs / ext4 remount,rw,errors=remount-ro,discard,noatime,data=ordered,nobarrier 0 1

Yes.. Replacing the eMMC chip/drive can be done. However, I don't have a good source for the original files..

Yes, or any other text editor. You will have to be root or use sudo, depending how your accessing the files to edit them. As Emerson has asked, why did the system stop working to begin with? Hardware going bad, power failure, a firmware update gone bad, something else? If the /etc/fstab is missing entries, what other files are missing data?

I am trying to copy the partitions including the boot partitions on the eMMC chip to a USB drive during "dd". The goal is to reload the partitions on a new eMMC chip. I have confirmed that partition 1 on the eMMC chip is corrupted. So, there is no need to copy that partition.

Here are the commands I am using in a Linux terminal window. However, in Windows using DiskInternals, I am not seeing the data on the USB drive.

dd if=/dev/mmcblk0boot0 of=/dev/sda1 conv=noerror,sync
dd if=/dev/mmcblk0boot1 of=/dev/sda1 conv=noerror,sync
dd if=/dev/mmcblk0p2 of=/dev/sda1 conv=noerror,sync
dd if=/dev/mmcblk0p3 of=/dev/sda1 conv=noerror,sync

FYI. I believe the bootloader/kernel is bzimage.

Here is my results from fdisk -l

~# fdisk -l
Disk /dev/mtdblock0: 16 MB, 16777216 bytes, 32768 sectors
2 cylinders, 255 heads, 63 sectors/track
Units: cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/mtdblock0 doesn't contain a valid partition table
Disk /dev/mtdblock1: 4 MB, 4194304 bytes, 8192 sectors
0 cylinders, 255 heads, 63 sectors/track
Units: cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/mtdblock1 doesn't contain a valid partition table
Disk /dev/mmcblk0: 7457 MB, 7820083200 bytes, 15273600 sectors
238650 cylinders, 4 heads, 16 sectors/track
Units: cylinders of 64 * 512 = 32768 bytes

Device Boot StartCHS EndCHS StartLBA EndLBA Sectors Size Id Type
/dev/mmcblk0p1 1023,3,16 1023,3,16 65536 12648448 12582913 6144M 83 Linux
/dev/mmcblk0p2 1023,3,16 1023,3,16 12648449 14745601 2097153 1024M 83 Linux
/dev/mmcblk0p3 1023,3,16 1023,3,16 14745602 14811138 65537 32.0M 83 Linux
Disk /dev/mmcblk0boot1: 4 MB, 4194304 bytes, 8192 sectors
128 cylinders, 4 heads, 16 sectors/track
Units: cylinders of 64 * 512 = 32768 bytes

Disk /dev/mmcblk0boot1 doesn't contain a valid partition table
Disk /dev/mmcblk0boot0: 4 MB, 4194304 bytes, 8192 sectors
128 cylinders, 4 heads, 16 sectors/track
Units: cylinders of 64 * 512 = 32768 bytes

Disk /dev/mmcblk0boot0 doesn't contain a valid partition table

If your attempting to dd each partition to the new chip without creating a partition table. won't work. You will need to create a partition table on the new chip with the partitions the exact same size as the old chip before dding each partition to the new chip. Option two is to DD the old chip to new chip, fix the bad partition on the the new chip and/or DD the old chip to a oldchip.img file to have a back up in case something goes wrong. DD the oldchip.img to new chip, fix the corrupted partition on the the new chip.