shred: 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/shred - from package: coreutils

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

On Debian possible default full paths are:

/usr/bin/shred - from package: coreutils

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

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