obprobe: 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/obprobe - from package: openbabel

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

On Debian possible default full paths are:

/usr/bin/obprobe - from package: openbabel

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

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