Hello
I wanted to share my awesome experience setting up my NAS, Synology DS214se (10 yrs old), DSM 7.1.1, cause it was just bananas
I started downgrading from DSM 7.1.1 to 6.2.4, which was so wrong cause it bricked the NAS, I couldn't access it in any way, no SSH, Telnet, browser interface.
I completely deleted the Kernel (zImage) from the chip, was so lucky I kept the HDD with the downgraded version of DSM.
At the end, I'll also tell you how I managed to let the NAS be accessed by DOS.
It's going to be a pretty long post, but I hope it'll help

This works for the versions of firmware that are formed from 3 files: uboot_something-something.bin, rd.bin and zImage

What you need, for Windows:
- USB 2 UART: CH341 or CH341A or CP2102. For CH341 to work on Serial (COM port), move jumper from 1-2 to 2-3
The COM port number will be shown in Device Manager -> Interface
Windows Update will install drivers for both of them, don't bother searching for drivers
- for UART: you'll connect the Rx from USB to Tx from the NAS and vice-versa and the GND-USB to GND-NAS
- an USB stick with ext2 partition (I made a 60MB partition), made in Linux, any Linux
- the zImage extracted from the .pat file of the OS (from the Synology download page)
- copy the zImage onto the USB's ext2 partition
- hopefully you'll still have the HDD with the downgrade version of DSM on it!!!
- I used Putty the entire time

Unbricking procedure (the double quotes are not needed,I used them to see the command better):
- connect the UART as explained above, the power cable and start the NAS
- when it says to press Ctrl+C (pay attention on the screen), do that
- the prompt will appear like this: ""Marvel>>""
- at ""Marvel>>"" insert ""resetenv"" and press enter. This will erase the zImage (kernel) from the NAS
I did this cause as you've seen above, it completly blocked me from accessing the NAS
- turn off the NAS and insert the USB with the zImage on it and the HDD with the downgraded version of
DSM (the one you used for downgrading)
- restart the NAS and now it will automatically enter into the ""Marvell>>"" prompt since the zImage (kernel) was erased
- use ""usb reset"" press enter
- then ""setenv usbActive 0"" and press enter (DS214se has USB ports only at the back, if you have front USB ports and want to
use them, insert 1 instead of 0)
- then use ""usb reset"" and press enter again, it should tell you that the USB stick is recognized
- then use ""ext2load usb 0:1 2159760 /zImage"" (this number 2159760, is the bytes size of the zImage)
also try without the slash / , in case it doesn't access it
- it should tell you that it read the file
- now use ""bootm"" command and press enter, it should start booting right into DSM now, DSM from the HDD
if it doesn't work, use ""bootm 0x2159760""
- now you can update the DSM version from the browser interface and during this the zImage (kernel) will also be rewritten onto
the firmware chip and you'll not need the USB stick anymore after this
- this is all I did. It seems easy but it took me days to figure this out, as I said, not an expert, learned on the way

This is how you can access the NAS (DS214se, DSM 7.1.1 in my case) from MS-DOS (even OS/2), using the LANMAN1 network protocol:

This is what I did in DSM 7.1.1:
- Control Panel
- File Services
- SMB Settings
- Enable SMB Service
- Advanced Settings
- General
- Minimum SMB protocol: SMB1
- Others
- Enable NTLMv1 authentication

- Control Panel
- Terminal & SNMP
- Enable Telnet service (port 23)
- Enable SSH service (port 22)
- Advanced Settings
- Low

- Control Panel
- Security
- Protection
- Enable auto block --debifat

Restart NAS

This is what I did using Putty with the SSH protocol:
- connect with Putty using your user and password
- insert this command line ""cd /etc/samba/"" (will get you into the Samba directory)
- then ""ls -ltr"" and you should see a file named ""smb.conf"". You are where you're supposed to
- enter and modify the file using ""sudo vi smb.conf""
- I think this is UNIX and for you to be able to modify it you have to press the Insert keyboard key or type "":i"" and press enter
- enter these 3 lines:
modify ""min protocol=NT1"" to ""min protocol=LANMAN1""
add ""ntlm auth=yes""
add ""lanman auth=yes""
- press ESC
- type "":wq"" and press enter. Done
- restart the NAS or use this command to restart the Samba server: ""sudo smbcontrol smbd reload-config""
I restarted the NAS, didn't try the restart Samba server command line
- create a new account and give it Read Only access (this what I did, I didn't want, by mistake, to delete files from DOS, W9x)
You can use your main account, as well, it doesn't matter.
- open Putty using SSH, log-in
- insert ""sudo cat /etc/samba/private/smbpasswd""
- this will be the answer:
""your account:a number:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:numbers and letters:whatever appears here""
This means that the hash for the password is not done and this is why you can't access the NAS from DOS, even though you
did all the steps from above
- it's time to create a hash for the password:
- insert ""sudo smbpasswd -L -U your username"" and press enter.
- it will ask you for a new password. I used the same one I entered in DSM. Now the hash is done
- to verify the hash use ""sudo cat /etc/samba/private/smbpasswd"" again and this should be the answer:
""your account:a number:numbers and letters:numbers and letters:whatever appears here""
- restart the NAS (I don't think it's obligatory but that's what I did)
- all done

For DOS, install Microsoft Network Client 3.0
After this, you can insert into the autoexec file this line "ping your IP from the router, NAS, etc"
It will ping your NAS, router, etc everytime you enter DOS
Connect with the user and password you chose
Use ""net view"" and will show you the entire network. If it errors, doesn't matter
Use ""net view \\your NAS name"" wait 5-10sec and it should connect showing you the shared folder
Use ""net use H: \\your NAS name\your shared folder"" to map it.
You can use whatever letter you want, H is an example

DO NOT CONNECT THE NAS TO THE INTERNET!!! after doing all of the above