capifaxrcvd: 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/capifaxrcvd - from package: isdn4k-utils

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

On Debian possible default full paths are:

/usr/sbin/capifaxrcvd - from package: capiutils

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

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