pfsextractchannels: 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/pfsextractchannels - from package: pfstools

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

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