rpmgraph: 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/bin/rpmgraph - from package: rpm-devel

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

On Debian possible default full paths are:

/usr/bin/rpmgraph - from package: rpm

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

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