pretty-bytes: 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/pretty-bytes - from package: nodejs-pretty-bytes

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

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