bat2gts: 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/bat2gts - from package: gerris-mpi
/usr/bin/bat2gts - from package: gerris

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

Error in other languages:
bat2gts: bevel nie gevind nie
bat2gts: comandă negăsită
bat2gts: comando não encontrado
bat2gts: commande introuvable
bat2gts: command not found
bat2gts: käsku ei ole
bat2gts: không tìm thấy lệnh
bat2gts: komanda nerasta
bat2gts: Kommando nicht gefunden.
bat2gts: kommandot finns inte
bat2gts: komut yok
bat2gts: nie znaleziono polecenia
bat2gts: níor aimsíodh an t-ordú
bat2gts: no se encontró la orden
bat2gts: no s'ha trobat l'ordre
bat2gts: opdracht niet gevonden
bat2gts: parancs nem található
bat2gts: perintah tidak ditemukan
bat2gts: príkaz nenájdený
bat2gts: příkaz nenalezen
bat2gts: команда не найдена
bat2gts: командата не е открита
bat2gts: 命令找不到
bat2gts: コマンドが見つかりません