qbrowser: 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/qbrowser - from package: qgis

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

On Debian possible default full paths are:

/usr/bin/qbrowser - from package: qgis-plugin-grass
/usr/bin/qbrowser - from package: qgis

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

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