lprng_index_certs: 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/lprng_index_certs - from package: lprng

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

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