ps2fax.gs: 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:

/var/spool/hylafax/bin/ps2fax.gs - from package: hylafax+-client

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

On Debian possible default full paths are:

/var/spool/hylafax/bin/ps2fax.gs - from package: hylafax-server

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

Error in other languages:
ps2fax.gs: bevel nie gevind nie
ps2fax.gs: comandă negăsită
ps2fax.gs: comando não encontrado
ps2fax.gs: commande introuvable
ps2fax.gs: command not found
ps2fax.gs: käsku ei ole
ps2fax.gs: không tìm thấy lệnh
ps2fax.gs: komanda nerasta
ps2fax.gs: Kommando nicht gefunden.
ps2fax.gs: kommandot finns inte
ps2fax.gs: komut yok
ps2fax.gs: nie znaleziono polecenia
ps2fax.gs: níor aimsíodh an t-ordú
ps2fax.gs: no se encontró la orden
ps2fax.gs: no s'ha trobat l'ordre
ps2fax.gs: opdracht niet gevonden
ps2fax.gs: parancs nem található
ps2fax.gs: perintah tidak ditemukan
ps2fax.gs: príkaz nenájdený
ps2fax.gs: příkaz nenalezen
ps2fax.gs: команда не найдена
ps2fax.gs: командата не е открита
ps2fax.gs: 命令找不到
ps2fax.gs: コマンドが見つかりません