kbookmarkmerger: 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/kbookmarkmerger - from package: kdebase

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

On Debian possible default full paths are:

/usr/bin/kbookmarkmerger - from package: kde-baseapps-bin

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

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