mimeopen: 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/mimeopen - from package: perl-File-MimeInfo

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

On Debian possible default full paths are:

/usr/bin/mimeopen - from package: libfile-mimeinfo-perl

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

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