grab-merge: 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/grab-merge - from package: ubuntu-dev-tools

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

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