shuf: 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/shuf - from package: coreutils

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

On Debian possible default full paths are:

/usr/bin/shuf - from package: coreutils

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

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