synce-serial-start: 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/synce-serial-start - from package: synce-serial

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

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