lftp: 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/lftp - from package: lftp

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

On Debian possible default full paths are:

/usr/bin/lftp - from package: lftp

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

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