1) Update OMV4 to latest version
2) In OMV create a user with a unique name and password, in this example User John with password Doe123
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3) Assign this user to group sambashare (and if you want this user also to be able to administrate OMV via SSH then also ssh and sudo groups):
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4) Create a new share using all defaults (maybe enable 'inherit permissions' if you know what you're doing):
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5) Enable SMB in OMV and choose as workgroup the same workgroup you use on your Win10 host (defaults to "WORKGROUP). All other settings are more or less irrelevant:
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6) Now the most important part: In Win10 start 'Credential Manager' and choose "Add a Windows Credential" where you now enter name of your OMV server -- rockpro64 in this case -- and John as well as Doe123 for the username and password values (simply the same you used when creating the user in OMV):
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7) Optional: to see how Credential Manager works open the command line and issue net view \\rockpro64 before and after you added your OMV user account to Credential Manager. Check the terminal window in the lower left for the difference between 'Access is denied' and listing the available shares after having added the account):
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8 ) Now that name resolution is confirmed to work and we ensured that logon credentials match it's time to 'Turn on network discovery and file sharing' if not already done:
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9) Your OMV server will now show up immediately if you installed all OMV4 updates and is ready to be accessed:
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10) Doubleclick the server name and choose one of the available shares (only one on my quick test install):
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11) To check whether access permissions are ok simply create a new directory:
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It's that easy. The most important part is to understand how authentication works with Win10 (Credentials Manager), how to debug simple problems like potential name resolution issues and to not let you confuse by crappy tutorials or strange advice the net and even this forum is flooded with.