syntax-validate: 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/sbin/syntax-validate - from package: 389-ds-base

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

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