keepassx: 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/keepassx - from package: keepassx

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

On Debian possible default full paths are:

/usr/bin/keepassx - from package: keepassx

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

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