amcheckdb: 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/amcheckdb - from package: amanda-server

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

On Debian possible default full paths are:

/usr/sbin/amcheckdb - from package: amanda-server

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

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