base64: 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/base64 - from package: coreutils

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

On Debian possible default full paths are:

/usr/bin/base64 - from package: coreutils

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

Error in other languages:
base64: bevel nie gevind nie
base64: comandă negăsită
base64: comando não encontrado
base64: commande introuvable
base64: command not found
base64: käsku ei ole
base64: không tìm thấy lệnh
base64: komanda nerasta
base64: Kommando nicht gefunden.
base64: kommandot finns inte
base64: komut yok
base64: nie znaleziono polecenia
base64: níor aimsíodh an t-ordú
base64: no se encontró la orden
base64: no s'ha trobat l'ordre
base64: opdracht niet gevonden
base64: parancs nem található
base64: perintah tidak ditemukan
base64: príkaz nenájdený
base64: příkaz nenalezen
base64: команда не найдена
base64: командата не е открита
base64: 命令找不到
base64: コマンドが見つかりません