openssl: 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/openssl - from package: openssl

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

On Debian possible default full paths are:

/usr/bin/openssl - from package: openssl

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

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