grainextract: 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/grainextract - from package: esys-particle

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

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