genaliases: 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/lib/mailman/bin/genaliases - from package: mailman

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

On Debian possible default full paths are:

/usr/lib/mailman/bin/genaliases - from package: mailman

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

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