tex: 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/tex - from package: texlive

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

On Debian possible default full paths are:

/usr/bin/tex - from package: texlive-binaries

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

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