snake-tree: 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/sbin/snake-tree - from package: snake

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

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