xcutsel: 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/xcutsel - from package: xorg-x11-apps

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

On Debian possible default full paths are:

/usr/bin/xcutsel - from package: x11-apps

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

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