synopsis: 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/synopsis - from package: synopsis

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

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