I am setting up my Ubuntu 14.04 server. I want to have an FTP access (I use vsftpd), mainly for my apache2 server, so I added a new user to the www-data group. I also set up the settings for vsftpd.conf, only allowing local users, and chroot_local_user=YES.I changed the home directory of my new user to /var/www/home. The permission are 755 (local_umask=022). I can now create files, download them in the /var/www/home/ directory and can not change to the root directory / on purpose for security reasons.But which strategy can I now use, when I want to change some conf files, download log files and so on, when I only allow the users to stay in their home directory? Which other security methods are highly recommend, to make my ftp server secure? 
ftp user for root directories?
linux;ubuntu;ftp;vsftpd
This is not how I would do this, but answering your question anyway:From man vsftpd.conf:chroot_list_enable      If  activated,  you  may  provide  a list of local users who are      placed in a chroot() jail in their home  directory  upon  login.      The meaning is slightly different if chroot_local_user is set to      YES. In this case, the list becomes a list of  users  which  are      NOT  to be placed in a chroot() jail.  By default, the file con      taining this list is /etc/vsftpd.chroot_list, but you may  over      ride this with the chroot_list_file setting.      Default: NOso:chroot_list_enable=YESchroot_list_file=/etc/vsftpd.chroot_listand add any user you don't want to be chrooted to that list so you can change some conf files, download log files and so on.