ocamlbuild: 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/ocamlbuild - from package: ocaml

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

On Debian possible default full paths are:

/usr/bin/ocamlbuild - from package: ocaml-nox

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

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