lefty: 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/lefty - from package: graphviz

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

On Debian possible default full paths are:

/usr/bin/lefty - from package: graphviz

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

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