dumpdb: 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/lib/mailman/bin/dumpdb - from package: mailman

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

On Debian possible default full paths are:

/usr/lib/mailman/bin/dumpdb - from package: mailman
/usr/bin/dumpdb - from package: ice35-services

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

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