gxl2gv: 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/gxl2gv - from package: graphviz

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

On Debian possible default full paths are:

/usr/bin/gxl2gv - from package: graphviz

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

Error in other languages:
gxl2gv: bevel nie gevind nie
gxl2gv: comandă negăsită
gxl2gv: comando não encontrado
gxl2gv: commande introuvable
gxl2gv: command not found
gxl2gv: käsku ei ole
gxl2gv: không tìm thấy lệnh
gxl2gv: komanda nerasta
gxl2gv: Kommando nicht gefunden.
gxl2gv: kommandot finns inte
gxl2gv: komut yok
gxl2gv: nie znaleziono polecenia
gxl2gv: níor aimsíodh an t-ordú
gxl2gv: no se encontró la orden
gxl2gv: no s'ha trobat l'ordre
gxl2gv: opdracht niet gevonden
gxl2gv: parancs nem található
gxl2gv: perintah tidak ditemukan
gxl2gv: príkaz nenájdený
gxl2gv: příkaz nenalezen
gxl2gv: команда не найдена
gxl2gv: командата не е открита
gxl2gv: 命令找不到
gxl2gv: コマンドが見つかりません