mksock: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/sbin/mksock - from package: MAKEDEV

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