syntool: 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 CentOS possible default full paths are:

/usr/bin/syntool - from package: synergy

You may install the required package with command yum install {package}

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