multixterm: 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/multixterm - from package: expectk

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

On Debian possible default full paths are:

/usr/bin/multixterm - from package: expect

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

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