syrthes-post: 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/syrthes-post - from package: syrthes-tools
/usr/lib/syrthes/bin/syrthes-post - from package: syrthes-tools

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

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