spectrwm: command not found

Have You tried accessing the binary with the full path?

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/spectrwm - from package: spectrwm

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