Quota and Swap

    Quota

    (If you have chosen a different partitioning scheme than I did, you must adjust this chapter so that quota applies to the partitions where you need it.)

    To install quota, we run this command:

    yum -y install quota

    Now we check if quota is already enabled for the filesystem where the website (/var/www) and maildir data (var/vmail) is stored. In this example setup, I have one big root partition, so I search for ' / ':

    mount | grep ' / '
    [root@web ~]# mount | grep ' / '

    /dev/vda1 on / type xfs (rw,relatime,attr2,inode64,noquota)

    If you have a separate /var partition, then use:

    mount | grep ' /var '

    instead. If the line contains the word "noquota", then proceed with the following steps to enable quota.

    Enabling quota on the / (root) partition

    Normally you would enable quota in the /etc/fstab file, but if the filesystem is the root filesystem "/", then quota has to be enabled by a boot parameter of the Linux Kernel.

    Edit the grub configuration file:

    nano /etc/default/grub

    search fole the line that starts with GRUB_CMDLINE_LINUX and add rootflags=uquota,gquota to the commandline parameters so that the resulting line looks like this:

    GRUB_CMDLINE_LINUX="vconsole.keymap=us selinux=0 net.ifnames=0 biosdevname=0 crashkernel=auto  vconsole.font=latarcyrheb-sun16 rhgb quiet rootflags=uquota,gq$
    GRUB_DISABLE_RECOVERY="true"

    and apply the changes by running the following command.

    cp /boot/grub2/grub.cfg /boot/grub2/grub.cfg_bak
grub2-mkconfig -o /boot/grub2/grub.cfg

    and reboot the server.

    reboot

    Now check if quota is enabled:

    mount | grep ' / '

    When quota is active, we can see "usrquota,grpquota" in the mount option list.

    Swap

    Swap space in Linux is used when the amount of physical memory (RAM) is full. If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space. While swap space can help machines with a small amount of RAM, it should not be considered a replacement for more RAM. Swap space is located on hard drives, which have a slower access time than physical memory. Swap space can be a dedicated swap partition (recommended), a swap file, or a combination of swap partitions and swap files. Note that Btrfs does not support swap space.

    yum install lvm2*

    lvmdiskscan

    You have three options:

    create a new swap partition
    create a new swap file
    extend swap on an existing LVM2 logical volume

    It is recommended that you extend an existing logical volume.

    Creating a Swap File

    To add a swap file:

    Determine the size of the new swap file in megabytes and multiply by 1024 to determine the number of blocks. For example, the block size of a 3GB swap file is 3145728KB

    1. Create an empty file:
      # dd if=/dev/zero of=/swapfile bs=1024 count=3145728
      Replace count with the value equal to the desired block size.
    2. Set up the swap file with the command:
      # mkswap /swapfile
    3. Change the security of the swap file so it is not world readable.
      # chmod 0600 /swapfile
    4. To enable the swap file at boot time, edit /etc/fstab as root to include the following entry:
      /swapfile          swap            swap    defaults        0 0
      The next time the system boots, it activates the new swap file.
    5. Regenerate mount units so that your system registers the new /etc/fstab configuration:
      # systemctl daemon-reload
    6. To activate the swap file immediately:
      # swapon /swapfile
    7. To test if the new swap file was successfully created and activated, inspect active swap space:
      $ cat /proc/swaps
$ free -h

    __--Deleting SWAP--__

    1. destroying swap_logic: swapoff /swapfile either swapoff -a
    2. nano /etc/fstab
      #/swapfile          swap            swap    defaults        0 0
    3. check settings: free -h
    4. execute following steps: systemctl daemon-reload(1) + reboot(2)
    5. verify a setting: free
    6. rm /swapfile

     

    Tuning Virtual Memory

    Virtual memory is typically consumed by processes, file system caches, and the kernel. Virtual memory utilization depends on a number of factors, which can be affected by the following parameters.
    swappiness
    A value from 0 to 100 which controls the degree to which the system favors anonymous memory or the page cache. A high value improves file-system performance, while aggressively swapping less active processes out of physical memory. A low value avoids swapping processes out of memory, which usually decreases latency, at the cost of I/O performance. The default value is 30.

    nano /etc/sysctl.conf

    vm.swappiness = 10
    vm.vfs_cache_pressure = 50

    cat /proc/sys/vm/vfs_cache_pressure

    cat /proc/sys/vm/swappiness

    Additional setting

     

    yum install psmisc
    fuser: command not found

    df -hP
    fdisk -l
    lvmdiskscan

    1. lsblk 
pvdisplay
    2.    pvscan
    3.    dd if=/dev/zero of=/dev/vdb bs=512 count=1
    4.  pvcreate /dev/vdb
    5.   lvmdiskscan
    6.   pvdisplay
    7.   pvscan
    8.    pvchange -x n /dev/vdb
    9.  pvchange -xy /dev/vdb
    10.  vgcreate volgroup /dev/vdb
    11.    vgs
    12.   vgdisplay volgroup
    13.    vgscan
    14.    lvcreate -L 10G volgroup
    15.  mkfs.xfs -b size=4k /dev/volgroup/lvol0
    16. mkdir /lvm_mount
    17. mount /dev/volgroup/lvol0 /lvm_mount
    18. /etc/fstab -----> UUID=50709e56-3823-4516-82b8-7cfa933e257f /lvm_mount xfs     defaults        1 2
      /dev/volgroup/lvol1
      UUID=55ed27b6-f77e-4233-a22e-637cf699907f
    19. pvscan
    20. lvcreate volgroup -n lvol1 -L 2.9G
    21. mkswap /dev/volgroup/lvol1
    22. nano /etc/fstab
      /dev/volgroup/lvol1   swap     swap    defaults     0 0
    23.  systemctl daemon-reload
    24. swapon -v /dev/volgroup/lvol1
    25. cat /proc/swaps
    26. free -h


    27. Sources:
      https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/ch-swapspace
      https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html-single/storage_administration_guide/#ch-fscache
      https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html-single/logical_volume_manager_administration/#logical_volumes


     sudo yum install cloud-utils-growpart

    2) sudo growpart /dev/sda 2

    3) sudo mount /dev/sda2 /mnt

    4) sudo xfs_growfs -d /mnt

    yum install xfsdump

    parted /dev/vda
    (parted) print
    (parted) resizepart 1 86%