sync_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/lib/cyrus/bin/sync_client - from package: cyrus-replication

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

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