spatialite_network: 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/bin/spatialite_network - from package: spatialite-bin

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