Ubuntu - Samba - Resolve rlimit_max below minimum Windows limit

Running the testparm command, which checks the Samba config file for errors, sometimes shows a message:

rlimit_max: increasing rlimit_max (1024) to minimum Windows limit (16384)

NOTE: This is just a warning.

On MS Windows the number of file handlers on the client and the server must be identical, else you will see the “too many files open” message when e. g. copying files over the network.
More recent Samba versions take care of this on their own.
However, if you want to remove this warning, you can do so by changing your local file limits.
It is always useful to distinguish local (user or session) limits and global (system wide) limits.

Check you global limits

cat /proc/sys/fs/file-max

result:

NOTE: Chances are good that your global limits far exceed your local limits.

sysctl -w fs.file-max=n

or permanently by editing /etc/sysctl.conf and running sysctl -p.

NOTE: Run these commands as the user which is running Samba.

Hard limits are enforced by the system:

To check the hard limits:

ulimit -Hn

result:

ulimit -Sn

result:

NOTE: This will show you hard and soft limits for the local session.

The hard limit is enforced by the system, while the soft limit is enforced by the local session.
You can increase the local soft limit up to the global hard limit, if necessary.

You can change the limits temporarily by running:

ulimit -Hn n
ulimit -Sn m

or you can set user limits via /etc/security/limits.conf and you can even specify for which users which limits apply, e. g.

samba soft nofile 16384
samba hard nofile 32768

NOTE: The man-pages of both files and the commands offer much more insight.