From SIPfoundry sipx, The Open Source SIP PBX for Linux - Calivia

Polycom phones come factory default to use FTP with a fixed user name and password. By using FTP, you can avoid the extra step of configuring each phone to use TFTP through the cumbersome dialpad.

NOTE: With this FTP setup which uses the default polycom password, it is no more secure or insecure as TFTP.

[edit] Automatic Setup of FTP

For sipX 3.6 users on Fedora, CentOS and Redhat, you can simply run

 yum install sipxconfig-ftp

to install and configure an FTP server w/default polycom credentials.

[edit] Manual Setup of FTP

Commands to install, start ftpd and start ftpd with system on reboot:

yum install vsftpd
chkconfig vsftpd on
service vsftpd start

If you installed from RPMs...

Create new user and change password, note capitalization:

# NOTE: 3.0 and Pingtel ECS customers should SIPXUSER=sipxchange
SIPXUSER=sipx \
  adduser -d /var/sipxdata/configserver/phone/profile/tftproot \
    -G $(SIPXUSER) -s /sbin/nologin -M PlcmSpIp
echo -e "PlcmSpIp" | sudo passwd --stdin PlcmSpIp

...or if you installed from source.

 adduser -d /usr/local/sipx/var/sipxdata/configserver/phone/profile/tftproot \
    -G $(SIPXPBXUSER) -s /sbin/nologin -M PlcmSpIp
 echo -e "PlcmSpIp" | sudo passwd --stdin PlcmSpIp

 ! NOTE ! If you installed from source, /var/sipxdata/configserver/phone/profile/tftproot should be /usr/local/sipx/var/sipxdata/configserver/phone/profile/tftproot