kfontview: 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/kfontview - from package: kdebase-workspace

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

On Debian possible default full paths are:

/usr/bin/kfontview - from package: kde-workspace-bin

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

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