plink: 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/plink - from package: putty

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

On Debian possible default full paths are:

/usr/bin/plink - from package: putty-tools

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

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