summer: 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/summer - from package: chiark-utils-bin

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

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