Problem Describe

Some times you are using web-content management software like WordPress, this problem might occur when uploading files or plugins installing. This solution is based on CybercitiFAQ

Make sure ftp server installed

Make sure ftp server installed and service is running. Under Debian Linux you can use dpkg command to verify that ftp server installed:

$ dpkg -l | grep -i "ftp"

OUTPUT

ii  ftp                               0.17-34.1                                amd64        classical file transfer client

OR run following command:

$ dpkg -l | grep -i ftp

RedHat using:

$ rpm -qa | grep -i "*ftp*"

Install under Ubuntu:

# apt-get install vsftpd

Is ftp server running (is port 21 open)?

$ telnet localhost 21

Edit the /etc/vsftpd/vsftpd.conf file

Open the file vim /etc/vsftpd/vsftpd.conf and find the following line, change NO to YES:

# Uncomment this to enable any form of FTP write command.
write_enable=YES

Set firewall to allow FTP:

$ sudo ufw allow ftp

and Port 21:

$ sudo ufw allow

Restart vsftpd

$ sudo systemctl restart vsftpd.service

If still not work, try to change the permission of your web-content-folder

$ chmod 755 [your web-content-folder]