opari2: 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/opari2 - from package: opari2

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

On Debian possible default full paths are:

/usr/bin/opari2 - from package: opari2

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

Error in other languages:
opari2: bevel nie gevind nie
opari2: comandă negăsită
opari2: comando não encontrado
opari2: commande introuvable
opari2: command not found
opari2: käsku ei ole
opari2: không tìm thấy lệnh
opari2: komanda nerasta
opari2: Kommando nicht gefunden.
opari2: kommandot finns inte
opari2: komut yok
opari2: nie znaleziono polecenia
opari2: níor aimsíodh an t-ordú
opari2: no se encontró la orden
opari2: no s'ha trobat l'ordre
opari2: opdracht niet gevonden
opari2: parancs nem található
opari2: perintah tidak ditemukan
opari2: príkaz nenájdený
opari2: příkaz nenalezen
opari2: команда не найдена
opari2: командата не е открита
opari2: 命令找不到
opari2: コマンドが見つかりません