eneconv: 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/eneconv - from package: gromacs

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

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