lmdemo: 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/bin/lmdemo - from package: levmar-devel

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

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