efax-gtk-socket-client: 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 Debian possible default full paths are:

/usr/bin/efax-gtk-socket-client - from package: efax-gtk

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

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