ftp: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/ftp - from package: ftp
/usr/lib/heimdal/bin/ftp - from package: heimdal-appl-clients
/usr/kerberos/bin/ftp - from package: krb5-appl-clients

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/ftp - from package: ftp.app

You may install the required package with command apt-get install {package}

Error in other languages:
ftp: bevel nie gevind nie
ftp: comandă negăsită
ftp: comando não encontrado
ftp: commande introuvable
ftp: command not found
ftp: käsku ei ole
ftp: không tìm thấy lệnh
ftp: komanda nerasta
ftp: Kommando nicht gefunden.
ftp: kommandot finns inte
ftp: komut yok
ftp: nie znaleziono polecenia
ftp: níor aimsíodh an t-ordú
ftp: no se encontró la orden
ftp: no s'ha trobat l'ordre
ftp: opdracht niet gevonden
ftp: parancs nem található
ftp: perintah tidak ditemukan
ftp: príkaz nenájdený
ftp: příkaz nenalezen
ftp: команда не найдена
ftp: командата не е открита
ftp: 命令找不到
ftp: コマンドが見つかりません