twadmin: 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/twadmin - from package: tripwire

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

On Debian possible default full paths are:

/usr/sbin/twadmin - from package: tripwire

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

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