cyclades-serial-client: 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/sbin/cyclades-serial-client - from package: cyclades-serial-client

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

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