ircd-mkpasswd: 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/sbin/ircd-mkpasswd - from package: ircd-irc2

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

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