ocamlopt.opt: 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/ocamlopt.opt - from package: ocaml

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

On Debian possible default full paths are:

/usr/bin/ocamlopt.opt - from package: ocaml-native-compilers

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

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