obgen: command not found

Have You tried accessing the binary with the full path?

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/obgen - from package: openbabel

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

On Debian possible default full paths are:

/usr/bin/obgen - from package: openbabel
/usr/lib/debug/usr/bin/obgen - from package: openbabel-dbg

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