apt-get install vsftpd

Add a user for ftp (or use an existing one and skip this step)

Add the created (or existing) user the “allowed users” of your vsftpd. Create the following file:

<your ftp user>

Configure the following settings in /etc/vsftpd.conf

The server doesnt start and the log shows the following error

failed to register local accounting service: File exists

Reason:
A file was created by root and cant be used by your non-root user

Fix:
Check for a cryptic files in /dev/shm/

#ls -al /dev/shm/
total 39228
drwxrwxrwt  2 root      root        1800 Dez  5 11:41 .
drwxr-xr-x 17 root      root        3640 Nov 13 06:47 ..
-rw-r--r--  1 root      root         128 Dez  5 11:41 7gbhujb54g8z9hu43jre8

rm /dev/shm/7gbhujb54g8z9hu43jre8

If you start teamspeak now, the file will be created with the correct user

ls -al /dev/shm/        total 39228
drwxrwxrwt  2 root      root         1800 Dez  5 12:10 .
drwxr-xr-x 17 root      root         3640 Nov 13 06:47 ..
-rw-r--r--  1 teamspeak teamspeak     128 Dez  5 12:10 7gbhujb54g8z9hu43jre8

https://forum.teamspeak.com/threads/93623-Instance-check-error-failed-to-register-local-accounting-service-on-Linux/page8