slappasswd: 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/sbin/slappasswd - from package: openldap-servers

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

On Debian possible default full paths are:

/usr/sbin/slappasswd - from package: slapd

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

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