• dovecot: imap(root@localhost)<3702>: Error: Mailbox INBOX: mmap(size=352609044) failed with file /var/spool/mail/root/Maildir/dovecot.index.cache: Cannot allocate memory


    If you get this error you may assume it is a lack of memory, which it could be, but more likely it is the default memory size of 256M. The file in this example was about 350M big which of course exceeds the virtual memory limits. This makes sense in smaller mail servers but if you have large amounts of users or e-mails this limit should be bumped. Check your default size limit: doveconf -n | grep -E 'vsz_limit|service imap' default_vsz_limi........
  • sysctl settings to reduce buffers and caches in Linux


    vm.swappiness = 1 vm.vfs_cache_pressure = 800 vm.dirty_ratio = 5 vm.dirty_background_ratio = 2 vm.min_free_kbytes = 65536 # Reserve 64MB for emergencies This is mainly useful for smaller systems/VMs/dev test/Raspberry Pi etc.. but even servers with huge amounts of RAM can start putting a ton of things into buffers and cache especially if you open large files constantly.........
  • Centos 7 not mounting /etc/fstab partitions


    If you are doing a custom deployment and image, make sure that when you rsync'd or tar'd that you didn't mess up the symlnk of /etc/mtab to /proc/self/mounts ln --force -s /proc/self/mounts /etc/mtab Will fix this........
  • OpenVZ vs LXC DIR mode poor security in LXC


    It is unfortunate that LXC's dir mode is completely insecure and allows way too much information from the host to be seen. I wonder if there will eventually be a way to break into the host filesystem or other container's storage? OpenVZ better security: [root@ev ~]# cat /proc/mdstat cat: /proc/mdstat: No such file or directory /dev/simfs 843G 740G 61G........
  • chroot in Linux Howto Simple and Easy Guide


    chroot which stands for change root allows you to virtually operate in another operating system even though you haven't booted it. It is commonly used to deploy new distros, applications and to fix a broken Linux/Unix install or prep a new system image without having to physically boot the drive or disk. So in this example let's say we have a drive that has a Linux OS installed on /dev/sdb1 and we have mounted this partition on /mnt/sdb1 The key point is to edit the &quo........
  • Centos 6 how to guide convert LVM non-RAID into mdadm 1/10 RAID array live without reinstalling


    Here is the scenario you or a client have a remote machine that was installed as a standard/default minimal Centos 6.x machine on a single disk with LVM for whatever reason. Often many people do not know how to install it to a RAID array so it is common to have this problem and why reinstall if you don't need to? In some cases on a remote system you can't easily reinstall without physical or KVM access. So in this case you add a second physical or disk or already ha........
  • Wordpress Custom Menu Limit Fix/Solution


    This is usually solved by two variables alone: max_input_vars=5000 memory_limit=256M Now you should be able to have unlimited amounts of custom menus in Wordpress.........
  • 95th Percentile Billing vs Usage Billing, what's better?


    There are all kinds of threads and links on the internet, and this seems to be a contentious issue butI don't know why. 95th percentile is either a good deal for some or a big rip off for others, Ijust said it there :) But the reality is that for MOST people who transfer low amounts of data but burst to higher speeds such as 40mbit+ even for short periods of time, then you'll pay a lot of money to do that. Basically 95th percentile is an-old archaic method........
  • FUSE/Curlftpfs mount ftp account as drive partition in Linux


    This is a great way to use your ftp server space, for example on your web hosting account (althoughI believe many hosts don't allow storage like this), but if you have a VPS/Dedicated Server etc.., this would be perfect. Imagine how easy it is to work with an ftp account that you can just mount as a normal partition or directory in Linux, it would be great for backups etc.. Name curlftpfs - mount a ftp host as a local directory Synopsis........
  • Convert HDD/Hard Drive Partition(s) into non-RAID into RAID 1 using existing data without data loss and without reformatting.


    Before we start I take no responsibility for this, you should have a backup and if you make a mistake during this process you could wipe out all of your data. So backup somewhere else before starting this as a precaution, or make sure it's data you could afford to lose. The RAID 1 Setup (Hardware Wise) I've already setup my 2 x 1TB (Seagate) drives with identical partitions, make sure your new hard drive (the empty one) is setup like your curr........
  • Clustered/Distributed Network Filesystems, Which Ones live up to the hype?


    I've tried to find a good sensible solution to cluster with and each technology has it's pros and cons and there is no perfect solution and I've found a lot of "exaggerations" in the applications, benefits and performance of these different filesystems. DRBD I first started off with DRBD and Ihave to say it does live up to the hype, is quite reliable (although it can be annoying to match up the kernel module and user applications since they must match and whe........
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