gem2gv: 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 Debian possible default full paths are:

/usr/bin/gem2gv - from package: ruby-graphviz

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

Error in other languages:
gem2gv: bevel nie gevind nie
gem2gv: comandă negăsită
gem2gv: comando não encontrado
gem2gv: commande introuvable
gem2gv: command not found
gem2gv: käsku ei ole
gem2gv: không tìm thấy lệnh
gem2gv: komanda nerasta
gem2gv: Kommando nicht gefunden.
gem2gv: kommandot finns inte
gem2gv: komut yok
gem2gv: nie znaleziono polecenia
gem2gv: níor aimsíodh an t-ordú
gem2gv: no se encontró la orden
gem2gv: no s'ha trobat l'ordre
gem2gv: opdracht niet gevonden
gem2gv: parancs nem található
gem2gv: perintah tidak ditemukan
gem2gv: príkaz nenájdený
gem2gv: příkaz nenalezen
gem2gv: команда не найдена
gem2gv: командата не е открита
gem2gv: 命令找不到
gem2gv: コマンドが見つかりません