installastheme: 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/installastheme - from package: afterstep

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

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