logwatch: 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/logwatch - from package: logwatch

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

On Debian possible default full paths are:

/usr/sbin/logwatch - from package: logwatch

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

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