This is a re-run of this question I asked two weeks ago, which was closed because it was related to an EOL Ubuntu version.

I did another install, this time on Ubuntu Server 20.04LTS, with exactly the same result. I also tried the same configuration on latest Debian (Buster 10.7), same result.

So, here we go :

The up-to-date Samba doc says (https://www.samba.org/samba/docs/current/man-html/smb.conf.5.html) :

When Samba 3.0 is configured to enable PAM support (i.e. --with-pam), this parameter will control whether or not Samba should obey PAM's account and session management directives.

Is this still supposed to work with Samba 4 ?

I had some strange result, it seems PAM's restrictions are enforced once, but then not anymore.

I tried to set up a file-size limitation on a Samba share. I'm not talking about quotas, I'm talking about preventing users from storing files that are bigger than 100MB, for example. I used /etc/security/limits.conf for this.

It almost works. Well, it works the first time a user tries to create a file, and then not anymore.

Here's what I did :

  • First I defined a hard filesize limit of 100MB for user johndoe in /etc/security/limits.conf :

    johndoe hard fsize 102400

  • Then I added session required pam_limits.so to /etc/pam.d/samba, in order to tell PAM to enforce the limitations

  • And finally, I added obey pam restrictions = yes to /etc/samba/smb.conf

At first it seemed promising, when user johndoe tries to copy a file > 100MB, a Windows 10 client throws the following error : An unexpected error is keeping you from copying the file...An unexpected network error occured

So far, so good ! That's what I wanted, prevent the user to store a file > 100MB

But if I click on "Try again", the file is copied anyway.

And if I then try to copy more files > 100MB, no more error message is thrown, and the copies proceed.

If user johndoe logs out and back in, same result : the first attempt at copying a file > 100MB throws an error, the following attempts succeed.

So, it seems the restriction I set in /etc/security/limits.conf is only enforced at the first attempt, and is no more enforced afterwards.

Any idea why ? Or any idea how I could achieve my goal (prevent a user to copy a file > 100MB) ?

1 Answer 1


OK I got a straight answer from the Samba team

Basically, to sum things up, setting up a limit for individual file size can not be done with Samba

The full discussion can be found in the february mailing list archive (https://lists.samba.org/archive/samba/2021-February.txt.gz)

  • Thanks for sharing the answer!
    – user535733
    Feb 11, 2021 at 0:19
  • But does this actually answer the question: Is “obey pam restrictions” still supposed to work in Samba 4 (Ubuntu 20.04)? If it does still work in Samba 4 then why does the documentation for obey pam restrictions still only mention Samba 3? May 3 at 18:56

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