ctfconvert: 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 Debian possible default full paths are:

/usr/bin/ctfconvert - from package: ctfutils

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

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