man2: 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/share/man/bin/man2 - from package: filesystem

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

Error in other languages:
man2: bevel nie gevind nie
man2: comandă negăsită
man2: comando não encontrado
man2: commande introuvable
man2: command not found
man2: käsku ei ole
man2: không tìm thấy lệnh
man2: komanda nerasta
man2: Kommando nicht gefunden.
man2: kommandot finns inte
man2: komut yok
man2: nie znaleziono polecenia
man2: níor aimsíodh an t-ordú
man2: no se encontró la orden
man2: no s'ha trobat l'ordre
man2: opdracht niet gevonden
man2: parancs nem található
man2: perintah tidak ditemukan
man2: príkaz nenájdený
man2: příkaz nenalezen
man2: команда не найдена
man2: командата не е открита
man2: 命令找不到
man2: コマンドが見つかりません