pure-ftpd: 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/sbin/pure-ftpd - from package: pure-ftpd

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

On Debian possible default full paths are:

/usr/sbin/pure-ftpd - from package: pure-ftpd

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

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