lppasswd: 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/lppasswd - from package: cups

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

On Debian possible default full paths are:

/usr/bin/lppasswd - from package: cups-client

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

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