nepomukbackup: 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/bin/nepomukbackup - from package: nepomuk-core-runtime

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

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