My thoughts

Étiquette : Linux

  • Troubles installing CentOS on XenServer

    You have a XenServer 6 or 7, and you have troubles installing CentOS (6 or 7) : the installer loads, but all you get is a black screen …

    This is a known issue, and I’m wondering why it wasn’t fixed because it’s there for so long.
    When having the boot menu, hit « tab » to show the option, and add the following :

    modprobe.blacklist=bochs_drm rhgb

    And then it worked !

    https://bugs.xenserver.org/browse/XSO-353

    https://discussions.citrix.com/topic/364226-centos-7-1503-installer-gives-blank-screen/

     

  • using a secured relay in Postfix

    I have a server on a LAN that need to send emails. Of course, this server has access to the internet through NAT, but for emails it is a bit more difficult : nowadays, email servers are checking many things when receiving emails : reverse, ‘from’ field, etc. and you may not have access to this kind of tuning for the internet IP address used with your NAT. So I needed to configure a relayhost, with direct access to the internet, that would accept my incoming email and relay it through normal channels. But I don’t want this server to be an open relay, so I have to setup authentication between them.

    (suite…)

  • Using auditd to troubleshoot file reads

    Today I will talk about auditd, a very powerfull tool to debug anything you need in a linux platform. In this very case, I had a problem with a mail server using all IO available. ‘iostat’ command told me it was reads ops that saturate it. A mail server has many process, so using « strace » is not helpful here. I choose to use auditd.

    (suite…)

  • Debugging a MySQL stall

    This article follows « finding an usual cause of max_user_connections ».
    After debugging a max_user_connections and a cache expiration problem in the customer app, we still experienced stalls of the mysqld process. MySQL refused all connections for 5 to 20 seconds, with no obvious reason. I’ll try to explain what I did to solve it.

    (suite…)

  • LVM attributes

    When you type ‘lvs’ on Linux, you get a list of logical volume system with their attributse as a single letter : /// LV VG Attr LSize Origin Snap% Move Log Copy% Convert lv_hdd hdd -wi-a- 232.00g /// We’ll explain all attr fields in this post.
    (suite…)