synclient: 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/synclient - from package: xorg-x11-drv-synaptics

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

On Debian possible default full paths are:

/usr/bin/synclient - from package: xserver-xorg-input-synaptics

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

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