yumdb: 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/yumdb - from package: yum-utils

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

On Debian possible default full paths are:

/usr/sbin/yumdb - from package: yum-utils

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

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