trjorder: 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/trjorder - from package: gromacs

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

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