kompare: 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/kompare - from package: kdesdk

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

On Debian possible default full paths are:

/usr/bin/kompare - from package: kompare

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

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