sfdp: 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/sfdp - from package: graphviz

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

On Debian possible default full paths are:

/usr/bin/sfdp - from package: graphviz

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

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