gnuclient.xemacs21: 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/gnuclient.xemacs21 - from package: xemacs21-bin

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

Error in other languages:
gnuclient.xemacs21: bevel nie gevind nie
gnuclient.xemacs21: comandă negăsită
gnuclient.xemacs21: comando não encontrado
gnuclient.xemacs21: commande introuvable
gnuclient.xemacs21: command not found
gnuclient.xemacs21: käsku ei ole
gnuclient.xemacs21: không tìm thấy lệnh
gnuclient.xemacs21: komanda nerasta
gnuclient.xemacs21: Kommando nicht gefunden.
gnuclient.xemacs21: kommandot finns inte
gnuclient.xemacs21: komut yok
gnuclient.xemacs21: nie znaleziono polecenia
gnuclient.xemacs21: níor aimsíodh an t-ordú
gnuclient.xemacs21: no se encontró la orden
gnuclient.xemacs21: no s'ha trobat l'ordre
gnuclient.xemacs21: opdracht niet gevonden
gnuclient.xemacs21: parancs nem található
gnuclient.xemacs21: perintah tidak ditemukan
gnuclient.xemacs21: príkaz nenájdený
gnuclient.xemacs21: příkaz nenalezen
gnuclient.xemacs21: команда не найдена
gnuclient.xemacs21: командата не е открита
gnuclient.xemacs21: 命令找不到
gnuclient.xemacs21: コマンドが見つかりません