lyx: 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/lyx - from package: lyx

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

On Debian possible default full paths are:

/usr/bin/lyx - from package: lyx

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

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