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/opt - from package: llvm

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

On Debian possible default full paths are:

/usr/bin/opt - from package: llvm
/usr/lib/llvm-3.4/bin/opt - from package: llvm-3.4
/usr/lib/llvm-3.5/bin/opt - from package: llvm-3.5

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

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