1. Httpd semaphores

    Recently we encountered some strange issues with httpd on some of our CentOS 7 machines during my current project.

    Through our pipeline we restart httpd several times which sometimes leads to this error:

    Apache: [error] (28)No space left on device
    

    After some research we found out the semaphores were all being used blocking httpd daemon to restart.

    The list of semaphores can be fetched by issuing

    # ipcs -st
    
    ------ Semaphore Operation/Change Times --------
    semid    owner      last-op                    last-changed
    753664   apache      Not set                    Mon Feb 17 20:20:47 2020
    786433   apache      Not set                    Mon Feb 17 20:20:47 …

  2. Btrfs mount issue

    I decided to bootstrap my new machine with btrfs as filesystem instead of ext4 LVM volumes. By following the excellent arch-wiki btrfs page I successfully crafted a base system with sub volumes, limited on size and snapshots enabled.

    Everything went fine, installed all the other stuff I needed, pulled in my data and was ready to go.

    Obviously on that very moment disaster happened.. Due to an unexpected interrupt the journal went corrupt. When trying to boot I got stuck right after decrypted the disk failing to mount my btrfs root volume.

    Uncool, unpleasant, .. I almost got insane..

    So back …


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