cmfetch: 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/cmfetch - from package: infernal

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

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