oarsh: 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/oarsh - from package: oar-common

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

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