regshell: 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 CentOS possible default full paths are:

/usr/bin/regshell - from package: samba4-client

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/regshell - from package: registry-tools

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

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