ext3grep: 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 Debian possible default full paths are:

/usr/bin/ext3grep - from package: ext3grep

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

Error in other languages:
ext3grep: bevel nie gevind nie
ext3grep: comandă negăsită
ext3grep: comando não encontrado
ext3grep: commande introuvable
ext3grep: command not found
ext3grep: käsku ei ole
ext3grep: không tìm thấy lệnh
ext3grep: komanda nerasta
ext3grep: Kommando nicht gefunden.
ext3grep: kommandot finns inte
ext3grep: komut yok
ext3grep: nie znaleziono polecenia
ext3grep: níor aimsíodh an t-ordú
ext3grep: no se encontró la orden
ext3grep: no s'ha trobat l'ordre
ext3grep: opdracht niet gevonden
ext3grep: parancs nem található
ext3grep: perintah tidak ditemukan
ext3grep: príkaz nenájdený
ext3grep: příkaz nenalezen
ext3grep: команда не найдена
ext3grep: командата не е открита
ext3grep: 命令找不到
ext3grep: コマンドが見つかりません