RNAcalibrate: 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/RNAcalibrate - from package: rnahybrid

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

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