calibredb: 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/calibredb - from package: calibre

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

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