dgrep: 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/dgrep - from package: debian-goodies

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

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