lpasswd: 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/lpasswd - from package: libuser

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

On Debian possible default full paths are:

/usr/sbin/lpasswd - from package: libuser

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

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