rhn-channel: 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/sbin/rhn-channel - from package: rhn-client-tools

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

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