lsmod: 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:

/sbin/lsmod - from package: module-init-tools

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

On Debian possible default full paths are:

/sbin/lsmod - from package: kmod
/bin/lsmod - from package: kmod

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

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