defmt-c: 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/defmt-c - from package: ispell

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

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