spip_add_site: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/spip_add_site - from package: spip

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