setserial: 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:

/bin/setserial - from package: setserial

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

On Debian possible default full paths are:

/bin/setserial - from package: setserial

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

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