Category Archives: Operating Systems

Linux : How to enable NTP loopfilter statistics on RHEL/CentOS?

You may end up at some point where you need detailed statistics about time synchronization on your Linux machine. To achieve that, simply do the following : 1. Edit your NTP configuration file :

2. Append the following parameters :

3. Restart the NTP daemon :

 

Windows : NTFS Warning The system failed to flush data to the transaction log. Corruption may occur.

Having repeated NTFS warning entries in EventViewer as the one below? Log Name: System Source: Ntfs Event ID: 57 Task Category: (2) Level: Warning Description: The system failed to flush data to the transaction log. Corruption may occur. This indicate an issue with the filesystem recovery mechanism and the filesystem might not be fault tolerant… Read More »

Linux : kernel httpd invoked oom-killer

You have noticed such behaviour in the system logs (/var/log/messages)? kernel: httpd invoked oom-killer: gfp_mask=0x201d2, order=0, oomkilladj=0 kernel: Call Trace: kernel: [<ffffffff800cb67d>] out_of_memory+0x8e/0x2f3 kernel: [<ffffffff8002e493>] __wake_up+0x38/0x4f kernel: [<ffffffff8000a7ea>] get_page_from_freelist+0x2/0x442 kernel: [<ffffffff8000f6a2>] __alloc_pages+0x27f/0x308 kernel: [<ffffffff8001308d>] __do_page_cache_readahead+0x96/0x17b kernel: [<ffffffff800139d6>] filemap_nopage+0x14c/0x360 kernel: [<ffffffff80008972>] __handle_mm_fault+0x1fd/0x103b kernel: [<ffffffff8000c795>] _atomic_dec_and_lock+0x39/0x57 kernel: [<ffffffff800671ae>] do_page_fault+0x499/0x842 kernel: [<ffffffff8005ddf9>] error_exit+0x0/0x84 Additionally, the system was hanging/very… Read More »

Linux : Binary location for [/usr/bin/host] in csf.conf is either incorrect, is not installed or is not executable

The following error may occur while reloading CSF (csf -r) : *WARNING* Binary location for [HOST] [/usr/bin/host] in /etc/csf/csf.conf is either incorrect, is not installed or is not executable *WARNING* Missing or incorrect binary locations will break csf and lfd functionality In this particular case, CSF was installed on a CentOS 7 server and there… Read More »