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

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

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