syslinux: 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/syslinux - from package: syslinux

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

On Debian possible default full paths are:

/usr/bin/syslinux - from package: syslinux

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

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