sig2dot: 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/sig2dot - from package: signing-party

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

Error in other languages:
sig2dot: bevel nie gevind nie
sig2dot: comandă negăsită
sig2dot: comando não encontrado
sig2dot: commande introuvable
sig2dot: command not found
sig2dot: käsku ei ole
sig2dot: không tìm thấy lệnh
sig2dot: komanda nerasta
sig2dot: Kommando nicht gefunden.
sig2dot: kommandot finns inte
sig2dot: komut yok
sig2dot: nie znaleziono polecenia
sig2dot: níor aimsíodh an t-ordú
sig2dot: no se encontró la orden
sig2dot: no s'ha trobat l'ordre
sig2dot: opdracht niet gevonden
sig2dot: parancs nem található
sig2dot: perintah tidak ditemukan
sig2dot: príkaz nenájdený
sig2dot: příkaz nenalezen
sig2dot: команда не найдена
sig2dot: командата не е открита
sig2dot: 命令找不到
sig2dot: コマンドが見つかりません