sssd: 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/sssd - from package: sssd-common

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

On Debian possible default full paths are:

/usr/sbin/sssd - from package: sssd-common

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

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