tomcat6: 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/sbin/tomcat6 - from package: tomcat6

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

Error in other languages:
tomcat6: bevel nie gevind nie
tomcat6: comandă negăsită
tomcat6: comando não encontrado
tomcat6: commande introuvable
tomcat6: command not found
tomcat6: käsku ei ole
tomcat6: không tìm thấy lệnh
tomcat6: komanda nerasta
tomcat6: Kommando nicht gefunden.
tomcat6: kommandot finns inte
tomcat6: komut yok
tomcat6: nie znaleziono polecenia
tomcat6: níor aimsíodh an t-ordú
tomcat6: no se encontró la orden
tomcat6: no s'ha trobat l'ordre
tomcat6: opdracht niet gevonden
tomcat6: parancs nem található
tomcat6: perintah tidak ditemukan
tomcat6: príkaz nenájdený
tomcat6: příkaz nenalezen
tomcat6: команда не найдена
tomcat6: командата не е открита
tomcat6: 命令找不到
tomcat6: コマンドが見つかりません