faxcover: 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/faxcover - from package: hylafax+-client

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

On Debian possible default full paths are:

/usr/bin/faxcover - from package: hylafax-client

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

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