links2: 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/links2 - from package: links

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

On Debian possible default full paths are:

/usr/bin/links2 - from package: links2

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

Error in other languages:
links2: bevel nie gevind nie
links2: comandă negăsită
links2: comando não encontrado
links2: commande introuvable
links2: command not found
links2: käsku ei ole
links2: không tìm thấy lệnh
links2: komanda nerasta
links2: Kommando nicht gefunden.
links2: kommandot finns inte
links2: komut yok
links2: nie znaleziono polecenia
links2: níor aimsíodh an t-ordú
links2: no se encontró la orden
links2: no s'ha trobat l'ordre
links2: opdracht niet gevonden
links2: parancs nem található
links2: perintah tidak ditemukan
links2: príkaz nenájdený
links2: příkaz nenalezen
links2: команда не найдена
links2: командата не е открита
links2: 命令找不到
links2: コマンドが見つかりません