Recent Posts

21

General Discussion / Resizing an Amazon EBS–backed Instance

« Last post by vaishakp on November 17, 2018, 09:45:14 pm »

To resize an Amazon EBS–backed instance

1. (Optional) If the new instance type requires drivers that are not installed on the existing instance, you must connect to your instance and install the drivers first.

2. Open the Amazon EC2 console.

3. In the navigation panel, choose Instances, and select the instance.

4. Choose Actions, select Instance State, and then choose Stop.

5. In the confirmation dialog box, choose Yes, Stop. It can take a few minutes for the instance to stop.

6. With the instance still selected, choose Actions, select Instance Settings, and then choose Change Instance Type. Note that this action is disabled if the instance state is not stopped.

7. In the Change Instance Type dialog box, do the following:

 a. From Instance Type, select the instance type that you want. If the instance type that you want does not appear in the list, then it is not compatible with the configuration of your instance (for example, because of virtualization type).

 b. (Optional) If the instance type that you selected supports EBS–optimization, select EBS-optimized to enable EBS–optimization or deselect EBS-optimized to disable EBS–optimization. Note that if the instance type that you selected is EBS–optimized by default, EBS-optimized is selected and you can't deselect it.

 c. Choose Apply to accept the new settings.

8. To restart the stopped instance, select the instance, choose Actions, select Instance State, and then choose Start.

9. In the confirmation dialog box, choose Yes, Start. It can take a few minutes for the instance to enter the running state.

22

General Discussion / Hardware Firewall : An Overview

« Last post by Vineesh K P on November 16, 2018, 06:47:01 pm »

What are Hardware Firewalls?

Everyone who has ever used a computer can probably tell you a story about being blocked in a firewall somewhere. Their function is surprisingly modest. They inspect traffic as it enters and leaves the computer and, based on some simple rules, either allow or deny that traffic. WindowsFirewall, UFW, IPTables, FirewallD: these are all examples of some of the most common names in this realm. A Hardware Firewall is just the same except it lives outside of the server.

A Hardware Firewall is a device which is entirely separate from your server. It has the same fundamental principle in that it inspects traffic and, based on the rule set configured, allows or denies traffic appropriately.

How Do Hardware Firewalls Work?

The hardware firewall is setup differently depending on your current configuration. The Firewall is situated outside your server and is connected directly to your uplink. If this is a new setup, the Firewall is then connected to your server. If this will be a new setup to a production server, a maintenance window would be scheduled to handle the physical connection. Once the connection to the server is established, all traffic to and from the server goes through the firewall, forcing it to pass inspection. This allows you to have granular control over the type of traffic you’re receiving, which is incredibly important.

23

General Linux / clamav uninstall

« Last post by arunlalpr on November 16, 2018, 11:48:28 am »

clamav uninstall

clamav uninstallation steps in different OS

1. Debian: # dpkg --remove clamav*
2. Redhat/Fedora: # yum remove clamav*
3. Mandriva: # urpme clamav
4. Gentoo: # emerge -C clamav
5. FreeBSD?: # pkg_deinstall -f security/clamav*
6. Slackware: # /etc/rc.d/rc.clamav stop; removepkg clamav

24

DirectAdmin / How to disable open_basedir in DirectAdmin

« Last post by arunlalpr on November 16, 2018, 11:42:28 am »

How to disable open_basedir in DirectAdmin

1. Log into Direct Admin panel as admin
2. Click on "PHP SafeMode Configuration" under Extra Features tab
3. Disable Open BaseDir for the domain.

That's it 

25

General Discussion / How to move /var folder to a new partition in Linux

« Last post by vaishakp on November 16, 2018, 05:10:17 am »

Your /var directory has filled up and you are left with no free disk space available. This is a typical scenario which can be easily fixed by mounting your /var directory on a different partition.


- make the new partition, & format with mkfs.ext3
- mount the new filesystem in /mnt

    #mkdir /mnt/newvar
    #mount /dev/sdb1 /mnt/newvar


- Go to single-user mode so that there is no rw activity on the directory during the process

    #init 1

- Backup data in var only (not the /var directory itself)

    #cd /var
    #cp -ax * /mnt/newvar

- Rename the /var directory (to make sure this has worked before deleting it!)

    #cd /
    #mv var var.old


- Make new var directory

    #mkdir /var

- Unmount the new partition

    #umount /dev/sdb1

- Remount it as /var

    #mount /dev/sdb1 /var

- If everything goes fine then put an entry into /etc/fstab

    /dev/sdb1               /var          ext3    defaults        0 0

Done.

26

General Discussion / How to block a spammer domain server wide on a cPanel server.

« Last post by joseletk on November 16, 2018, 02:02:35 am »

Create a file named /etc/eximblacklist and add the entry "domainname.com" (without quotes). That is, add the domains you need to blacklist.

Next, we need to open the Exim configuration file /etc/exim.conf

Add the below lines in the first section just below the line "#!!# cPanel Exim 4 Config"

Code: [Select]

domainlist exim_blacklist = lsearch;/etc/eximblacklist
Now add inside the section under "ROUTERS CONFIGURATION"

Code: [Select]

reject_domains:

driver = redirect
# RBL Blacklist incoming hosts
domains = +exim_blacklist
allow_fail
data = :fail: Connection rejected: SPAM source $domain is manually blacklisted.

Save the configuration and see the Exim error log. You can see the domain blocked.

We can add more domain manually to reject more if domains sending spam.

27

General Linux / Change the Default Kernel in CentOS7 (GRUB2)

« Last post by Vineesh K P on November 15, 2018, 07:58:58 pm »

Hello all,

In this post, we will check how to change the default kernel in CentOS with GRUB2, we will try to boot with an old kernel. So, let's get started.

GRUB2 is the most common bootloader for RHEL 7 systems. A symlink to the GRUB2 config file should be present at /etc/grub2.cfg.

By default, the value for the directive GRUB_DEFAULT in the /etc/default/grub file is “saved”.

Code: [Select]

# cat /etc/default/grub
GRUB_TIMEOUT=5
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="nomodeset crashkernel=auto rd.lvm.lv=vg_os/lv_root rd.lvm.lv=vg_os/lv_swap rhgb quiet"
GRUB_DISABLE_RECOVERY="true"

This instructs GRUB 2 to load the kernel specified by the saved_entry directive in the GRUB 2 environment file, located at /boot/grub2/grubenv.

Code: [Select]

# cat /boot/grub2/grubenv
# GRUB Environment Block
saved_entry=Red Hat Enterprise Linux Server (3.10.0-327.10.1.el7.x86_64) 7.2 (Maipo)
One can set another GRUB record to be the default, using the grub2-set-default command, which will update the GRUB 2 environment file. By default, the saved_entry value is set to the name of latest installed kernel of package type kernel. This is defined in /etc/sysconfig/kernel by the UPDATEDEFAULT and DEFAULTKERNEL directives.

Code: [Select]

# cat /etc/sysconfig/kernel
# UPDATEDEFAULT specifies if new-kernel-pkg should make
# new kernels the default
UPDATEDEFAULT=yes

# DEFAULTKERNEL specifies the default kernel package type
DEFAULTKERNEL=kernel

# MAKEDEBUG specifies if new-kernel-pkg should create non-default
# "debug" entries for new kernels.
MAKEDEBUG=yes
To force a system to always use a particular menu entry, use the menu entry name as the key to the GRUB_DEFAULT directive in the /etc/default/grub file. The following command will print a list of the menu entries present in GRUB2’s configuration.

Code: [Select]

# awk -F\' /^menuentry/{print\$2} /etc/grub2.cfg
Red Hat Enterprise Linux Server (3.10.0-327.10.1.el7.x86_64) 7.2 (Maipo)                          ===> entry 0
Red Hat Enterprise Linux Server (3.10.0-229.el7.x86_64) 7.2 (Maipo)                               ===> entry 1
Red Hat Enterprise Linux Server (0-rescue-0cb6313ed65e4b36ba5daace11f3ad50) 7.2 (Maipo)           ===> entry 2
GRUB 2 supports using a numeric value as the key for the saved_entry directive to change the default order in which the kernel or operating systems are loaded. To specify which kernel should be loaded first, pass its number to the grub2-set-default command. The IDs are assigned in order the menu entries appear in the /etc/grub2.cfg file starting with 0. So the kernel 3.10.0-229.el7.x86_64 get an ID of 1.

Code: [Select]

# grub2-set-default 1
Check the below file to see the kernel which will be loaded at next boot, crosscheck the numeric value with the menu entry in the /etc/default/grub file.

Code: [Select]

# cat /boot/grub2/grubenv |grep saved
saved_entry=1
Changes to /etc/default/grub require rebuilding the grub.cfg file as follows:

Code: [Select]

# grub2-mkconfig -o /boot/grub2/grub.cfg

Once you have verified everything and rebuilt the GRUB2 configuration file, you can go ahead an reboot the server for changes to take effect.

Code: [Select]

shutdown -r now

28

General Windows / Ansible on Windows

« Last post by arunlalpr on November 15, 2018, 04:21:55 pm »

Ansible on Windows

We can now manage windows machine using Ansible.

For that, we need to install the following setup in our windows machine.

===========
1. Install Python-winrm to allow Ansible to connect to the Windows machines
2. Upgrade to PowerShell 3.0+ to support Windows modules
3. Enable Windows remoting so that Ansible can connect
============

Windows machines are created the same way as all the other machines that you have
in your inventory.

They are differentiated by the value of the ansible_connection variable.

When ansible_connection is set to winrm , it will try to connect via winrm to Windows PowerShell on the remote machine.

Ansible also uses the ansible_ssh_user , ansible_ssh_pass , and ansible_ssh_port values like it would on your other machine.

However, they use ssh in them, actually try to connect to Windows PowerShell Remoting service by using the
credentials.

 [windows]
test.domain.com
win01.domain.com
win02.domain.com


[windows:vars]
ansible_connection=winrm
ansible_ssh_user=tom
ansible_ssh_pass=s3cr3t
ansible_ssh_port=5757


You can check the connection by using


ansible win01.domain.com -u tom -m win_ping

If everything works correctly, you should see the following output:

===========

win01.domain.com | success >> {
"changed": false,
"ping": "pong"
}

============

That's it Try the same your end and let us know the result

29

General Linux / How to check raid configuration in linux server

« Last post by arunlalpr on November 13, 2018, 06:24:19 pm »

How to check raid configuration in linux server

Run the following command :

cat /proc/mdstat

====================
[root@213 ~]# cat /proc/mdstat
Personalities : [raid1]
md2 : active raid1 sdd3[1] sdc3[0]
      1952331776 blocks super 1.2 [2/2] [UU]
      bitmap: 0/15 pages [0KB], 65536KB chunk

md0 : active raid1 sdb2[1] sda2[0]
      523264 blocks super 1.2 [2/2] [UU]
      bitmap: 0/1 pages [0KB], 65536KB chunk



md1 : active raid1 sdb3[1] sda3[0]
      123917312 blocks super 1.2 [2/2] [UU]
      bitmap: 1/1 pages [4KB], 65536KB chunk

unused devices: <none>

=========================

That's it 

30

General Linux / Why use BSD over Linux

« Last post by Vineesh K P on November 13, 2018, 06:34:36 am »

In this article, we will look at some of the reasons why people are using BSD over Linux.

1. Packages are More Trustworthy

Speaking of packages, another point that the BSD users raised was the trustworthiness of packages. In BSD, all packages are provided by “a centralized package/ports system with every package getting built as part of a single repository with security systems in place each step of the way”. This ensures that a hacker can’t sneak malicious software into a seemingly-safe application and lends to the long-term stability of BSD.

2. Slow Change = Better Long-Term Stability

In the BSD world, major releases take longer. This means that there is more of a focus on getting things right then getting them pushed out to the user. This also means that changes to the operating system happen over time. Like with Debian, long development cycles help BSD to test new ideas to make sure they work properly before making them permanent. It also helps to produce code less likely to have issues.

3. Linux is Too Cluttered

When it came to choosing which BSD they were going to use, the choice was fairly easy. There are only half a dozen BSDs that are being actively developed. Of those BSDs, each one has a specific purpose. “OpenBSD security, FreeBSD more desktop/server, NetBSD “run on anything and everything”, DragonFlyBSD scaling and performance.” Meanwhile, the Linux world is full of distros that just add a theme or icon pack to an existing distro. The smaller number of BSD projects means that there is less duplication of effort and more overall focus.

4. ZFS Support

One BSD user noted that one of the main reasons that he switched to BSD was ZFS. In fact almost all of the people I talked to mentioned ZFS support on BSD as the reason they did not return to Linux.

This is an area where Linux will lose out on for the time being. While OpenZFS is available on some Linux distros, ZFS is built into the BSD kernels. This alone means that ZFS will have better performance on BSD. While there have been several attempts to get ZFS into the Linux kernel, licensing issues will be solved first.

5. License

There was also a difference of opinion on licenses. The general idea held by many is the GPL is not truly free because it put limits on how you can make use of the software. Some also think that the GPL is “too large and difficult to interpret which can lead to legal problems down the road if a person is not careful when developing a product with this license”.

On the other hand, the BSD license only has three clauses and allows anyone to “take the software, make changes, and do whatever you want with it, but it also offers protection to the developer”.