From log:
useradd: cannot lock /etc/passwd; try again later. adduser: `/usr/sbin/useradd -d /srv/ftp -g ftp -s /bin/false -u 148 ftp' returned error code 1. Exiting. dpkg: error processing vsftpd (--configure): subprocess installed post-installation script returned error exit status 1
From log:
useradd: cannot lock /etc/passwd; try again later.
adduser: `/usr/sbin/useradd -d /srv/ftp -g ftp -s /bin/false -u 148 ftp' returned error code 1. Exiting.
dpkg: error processing vsftpd (--configure):
subprocess installed post-installation script returned error exit status 1