Monday, 21 January 2019


1) rpm -Uvh

If this is already installed, skip this step.

2) yum install fail2ban

3) if any error occur, clean yum and install fail2ban again by executing these command again.

        yum clean all
    yum install fail2ban

4) If fail2ban installation is successfull.

cd /etc/fail2ban/

5) You cannot make any changes to "jail.conf" file. So make a copy of this file as "jail.local"

cp jail.conf jail.local

6) Open this file using any of your editor. I prefer vi editor.

vi jail.local

7) In this file , under ssh-iptables heading, it will be shown like this as below


enabled  = false
filter   = sshd
action   = iptables[name=SSH, port=ssh, protocol=tcp]
           sendmail-whois[name=SSH, dest=root,]
logpath  = /var/log/secure
maxretry = 5

8) Change enabled parameter of ssh-iptables to true.

Set maxretry parameter to any integer. If any user import incorrect ssh key beyond this limit, ip address of that user will be banned for your server. I have given 5 here.

You can also get mail when any ip get banned by setting "dest" and "sender" parameter for "sendmail-whois".

Give the complete path of the login details log file in logpath parameter.

9) Finally, restart fail2ban.

sudo service fail2ban restart

10) U can verify if ssh fail2ban is successfully started its service by typing this command,

iptables -L

It will show like this if fail2ban ssh is successfullt installed.

Chain INPUT (policy ACCEPT)
target     prot opt source               destination
fail2ban-SSH  tcp  --  anywhere             anywhere            tcp dpt:ssh

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Chain fail2ban-SSH (1 references)
target     prot opt source               destination
RETURN     all  --  anywhere             anywhere

11) You can set your ssh fail2ban reg expression.

cd filter.d/
vi sshd.conf

12) Please do include following ssh failregex expression in sshd.conf file.

^%(__prefix_line)s(?:error: PAM: )?[aA]uthentication (?:failure|error) for .* from <HOST>( via \S+)?\s*$
            ^%(__prefix_line)s(?:error: PAM: )?User not known to the underlying authentication module for .* from <HOST>\s*$
            ^%(__prefix_line)sFailed \S+ for .*? from <HOST>(?: port \d*)?(?: ssh\d*)?(: (ruser .*|(\S+ ID \S+ \(serial \d+\) CA )?\S+ %(__md5hex)s(, client user ".*", client host ".*")?))?\s*$
            ^%(__prefix_line)sROOT LOGIN REFUSED.* FROM <HOST>\s*$
            ^%(__prefix_line)s[iI](?:llegal|nvalid) user .* from <HOST>\s*$
            ^%(__prefix_line)sUser .+ from <HOST> not allowed because not listed in AllowUsers\s*$
            ^%(__prefix_line)sUser .+ from <HOST> not allowed because listed in DenyUsers\s*$
            ^%(__prefix_line)sUser .+ from <HOST> not allowed because not in any group\s*$
            ^%(__prefix_line)srefused connect from \S+ \(<HOST>\)\s*$
            ^%(__prefix_line)sReceived disconnect from <HOST>: 3: \S+: Auth fail$
            ^%(__prefix_line)sReceived disconnect from <HOST>: 11: $
            ^%(__prefix_line)sReceived disconnect from <HOST>: 11: User exit$
            ^%(__prefix_line)sReceived disconnect from <HOST>: 14: No supported authentication methods available$
            ^%(__prefix_line)sReceived disconnect from <HOST>: 14: no authentication methods available$
            ^%(__prefix_line)sUser .+ from <HOST> not allowed because a group is listed in DenyGroups\s*$
            ^%(__prefix_line)sUser .+ from <HOST> not allowed because none of user's groups are listed in AllowGroups\s*$
            ^%(__prefix_line)sConnection closed by <HOST>$

13) You can check all ssh  fail2ban failregex with your previous user login log file :

fail2ban-regex /var/log/secure /etc/fail2ban/filter.d/sshd.conf

Sunday, 20 January 2019

ldap server linux

1) Setup networking. (Both IP should ping with each other and should be able to ssh each other and selinux should be disabled and firewalld should be disabled)
2) setup hostname of server :- (/etc/hostname :- make entry
3) Setup client hostname:-
4) /etc/resolv.conf or /etc/hosts :-
ip server
ip client

A) At server End:- 
# yum install openldap* migrationtools -y

B) Configure Ldap password:-
# slappasswd

C) Configure Ldap server file:-

# cd /etc/openldap/slapd.d/cn=config
# vim olcDatabase={2}.hbd.ldif

olcSuffix dc=mydomain,dc=com
oldRootDN cn=Manager dc=mydomain,dc=com

and add following lines below:-

olcRootPW = {SSHA} (password generated by slappasswd command)
olcTLSCertificateFile = /etc/pki/tls/certs/mydomainldap.pem
olcTLSCertificateKeyFile = /etc/pki/tls/certs/mydomainldapkey.pem

D) Provide Monitoring Privileges
# vim olcDatabase={1}Monitor.ldif
change here dc=mydomain,dc=com

E) Verify the Configuration:-
# slaptest -u

F) Start and enable ldap service:-
# service slapd start
# service slapd enable
# netstat -tunlp | grep 389 (389 is ldap port number or we can also grep ldap service)

G) Configure Ldap Database 
# cp /usr/share/openldap-servers/DB_CONFIG.example /var/lib/ldap/DB_CONFIG
# chown -R ldap. /var/lib/ldap/
# ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/openldap/schema/cosine.ldif
# ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/openldap/schema/nis.ldif
# ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/openldap/schema/inetorgperson.ldif

H) Create Self Signed Certificates:- 
# openssl -new -x509 -nodes -out /etc/pki/tls/certs/mydomailldap.pem -keyout /etc/pki/tls/certs/mydomainldapkey.pem -days 365
# ls -lrth /etc/pki/tls/certs/*.pem (to check certicates)

I) Create Base object:-
# cd /usr/share/migrationtools/
# vim
line 71

line 74
$DEFAULT_BASE = "dc=mydomain,dc=com"

line 90


# vim /root/base.ldif
dn: dc=mydomain,dc=com
objectclass: top
objectclass: object
objectclass: organization
o: mydomain com
dc: mydomain

dn: cn=Manager dc=mydomain,dc=com
objectclass: organizationRole
cn: Manager
description: Directory Manager

dn: ou=People,dc=mydomain,dc=com
objectClass: organizationUnit
ou: People

dn: ou=Group,dc=mydomain,dc=com
ObjectClass: organizationUnit
ou: Group

K) User add and give password
# useradd ldapuser1
# echo "redhat" | passwd --stdin ldapuser1

L) make manually file from /etc/passwd file (TAKE ALL USERS RATHER THAN SYSTEM USERS AND ENTER IN SEPRATE FILE)
grep ":10[0-9][0-9]" /etc/passwd > /root/passwd

M) Import and Migrate local user Database to LDAP Database
# ./ /root/group /root/group.ldif
# ./ /root/passwd /root/users.ldif

# ldapadd -x -W -D "cn=Manager dc=mydomain,dc=com" -f /root/base.ldif
# ldapadd -x -W -D "cn=Manager dc=mydomain,dc=com" -f /root/users.ldif
# ldapadd -x -W -D "cn=Manager dc=mydomain,dc=com" -f /root/groups.ldif

(note:- It will ask for password for Manager. at time of slappasswd creation which converted to hashed password)

N) Test the configuration:- search created users like we are searching for ldapuser1

# ldapsearch -x cn=ldapuser1 -b dc=mydomain,dc=com
# ldapsearch -x -b 'dc=mydomain,dc=com' '(objectclass=*)'
# service firewalld stop

O) Configure NFS Server for directory sharing:-

# vim /etc/exports
/home *(rw,sync)

# yum install rpcbind nfs-utils
# service nfs start
# service rpcbind start
# service nfs enable
# service rpcbind enable

P) test mounting:-
# showmount -e

Configre Client :-

A) client install
# yum install openldap-clients nss-pam-ldapd
# authconfig-tui (If it is not installed then install authconfig-gtk package)

B) configure server setting at client end:-
# authconfig-tui
1 Put * mark on  USE LDAP:-  [*] USE LDAP
3 Select Next and Enter
4 Enter Server Filed:- ldap://
5 Enter Base DN Field as "dc=mydomain,dc=com"
6 Select Ok and then Enter

C) Test Client Configuration:- Search for the ldap user by below command, if you are getting response then our ldap client configuration is working fine.

# getent passwd ldapuser1

D) Mount LDAP Users Home Directory on Client machine:-
# vim /etc/fstab /home auto defaults 0 0

# mount -a (to permanently mount and test the mount file if it will give error like no mount format then restart nfs on server side)

# su ldapuser1 (it should login with ldapuser1 on server)

Wednesday, 26 December 2018

sip unreachable alerts

If sip unreachable then send auto mail

vim /home/

DATE=`date "+%d.%m.%Y. %H:%M"`
Status=`/usr/sbin/asterisk -rx "sip show peers" |grep UNREACHABLE`
SIP=`/usr/sbin/asterisk -rx "sip show peers" |grep UNREACHABLE |wc -l`

if [ $SIP -gt 1 ]
echo -e "$Status" | mail -s "SIP Peer Unreachable `hostname` $DATE"
echo $Status
   echo "None of the condition met"

Then set in crontab

crontab -e

* * * * * /bin/sh /home/


Sunday, 16 December 2018

Step-by-step OpenLDAP Installation and Configuration on server

Step by Step Installation and Configuration OpenLDAP Server
openldap 2.2.13-6.4E
System name:
Domain name:
System IP:
Note: Use your domain name and IP instead of xyz.
Easy steps for adding users:
    1. Create unix user
    2. Create unix user’s ldap passwd file
    3. Convert passwd.file to ldif file
    4. Add ldap file to LDAP Directory using ldapadd
Step #1. Requirements
    compat-openldap.i386 0:2.1.30-6.4E
    openldap-clients.i386 0:2.2.13-6.4E
    openldap-devel.i386 0:2.2.13-6.4E
    openldap-servers.i386 0:2.2.13-6.4E
    openldap-servers-sql.i386 0:2.2.13-6.4E
You can install them using the command:
yum install *openldap* -y
Step #2. Start the service
[root@ldap ~]# chkconfig –levels 235 ldap on
[root@ldap ~]# service ldap start
Step #3. Create LDAP root user password
[root@ldap ~]# slappasswd
    New password:
    Re-enter new password:
[root@ldap ~]#
Step #4. Update /etc/openldap/slapd.conf for the root password
[root@ldap ~]# vi /etc/openldap/slapd.conf
    #68 database        bdb
    #69 suffix          “dc=xyz,dc=com”
    #70 rootdn          “cn=Manager,dc=xyz,dc=com”
    #71 rootpw          {SSHA}cWB1VzxDXZLf6F4pwvyNvApBQ8G/DltW
Step #5. Apply Changes
[root@ldap ~]# service ldap restart
Step #6. Create test users
[root@ldap ~]# useradd test1
[root@ldap ~]# passwd test1
    Changing password for user test1.
    New UNIX password:
    Retype new UNIX password:
    passwd: all authentication tokens updated successfully.
[root@ldap ~]# useradd test2
[root@ldap ~]# passwd test2
    Changing password for user test2.
    New UNIX password:
    Retype new UNIX password:
    passwd: all authentication tokens updated successfully.
[root@ldap ~]#
Note: Repeat the same for the rest of users
Step #7. Migrate local users to LDAP
[root@ldap ~]# grep root /etc/passwd > /etc/openldap/passwd.root
[root@ldap ~]# grep test1 /etc/passwd > /etc/openldap/passwd.test1
[root@ldap ~]# grep test2 /etc/passwd > /etc/openldap/passwd.test2
 Note: Repeat the same for the rest of users
Step #8. Update default settings on file /usr/share/openldap/migration/
    #71 $DEFAULT_MAIL_DOMAIN = “”;
    #74 $DEFAULT_BASE = “dc=xyz,dc=com”;
Step #9. Convert passwd.file to ldif (LDAP Data Interchange Format) file
[root@ldap ~]# /usr/share/openldap/migration/ /etc/openldap/passwd.root /etc/openldap/root.ldif
[root@ldap ~]# /usr/share/openldap/migration/ /etc/openldap/passwd.test1 /etc/openldap/test1.ldif
[root@ldap ~]# /usr/share/openldap/migration/ /etc/openldap/passwd.test2 /etc/openldap/test2.ldif
Note: Repeat the same for the rest of users
Step #10. Update root.ldif file for the “Manager” of LDAP Server
[root@ldap ~]# vi /etc/openldap/root.ldif
    #1 dn: uid=root,ou=People,dc=xyz,dc=com
    #2 uid: root
    #3 cn: Manager
    #4 objectClass: account
Step #11. Create a domain ldif file (/etc/openldap/
[root@ldap ~]# cat /etc/openldap/
    dn: dc=xyz,dc=com
    dc: xyz
    description: LDAP Admin
    objectClass: dcObject
    objectClass: organizationalUnit
    ou: rootobject
    dn: ou=People, dc=xyz,dc=com
    ou: People
    description: Users of xyz
    objectClass: organizationalUnit
Step #12. Import all users in to the LDAP
Add the Domain ldif file
[root@ldap ~]# ldapadd -x -D “cn=Manager,dc=xyz,dc=com” -W -f  /etc/openldap/
    Enter LDAP Password:
    adding new entry “dc=xyz,dc=com”
    adding new entry “ou=People, dc=xyz,dc=com”
[root@ldap ~]#
Add the users:
[root@ldap ~]# ldapadd -x -D “cn=Manager,dc=xyz,dc=com” -W -f  /etc/openldap/root.ldif
    Enter LDAP Password:
    adding new entry “uid=root,ou=People,dc=xyz,dc=com”
    adding new entry “uid=operator,ou=People,dc=xyz,dc=com”
[root@ldap ~]#
[root@ldap ~]# ldapadd -x -D “cn=Manager,dc=xyz,dc=com” -W -f  /etc/openldap/test1.ldif
    Enter LDAP Password:
    adding new entry “uid=test1,ou=People,dc=xyz,dc=com”
[root@ldap ~]#
[root@ldap ~]# ldapadd -x -D “cn=Manager,dc=xyz,dc=com” -W -f  /etc/openldap/test2.ldif
    Enter LDAP Password:
    adding new entry “uid=test2,ou=People,dc=xyz,dc=com”
 [root@ldap ~]#
 Note: Repeat the same for the rest of users
Step #13. Apply Changes
[root@ldap ~]# service ldap restart
Step #14. Test LDAP Server
It prints all the user information:
[root@ldap ~]# ldapsearch -x -b ‘dc=xyz,dc=com’ ‘(objectclass=*)’

LDAP-based Authentication in RHEL

As we will see, there are several other possible application scenarios, but in this guide we will focus entirely on LDAP-based authentication. In addition, please keep in mind that due to the vastness of the subject, we will only cover its basics here, but you can refer to the documentation outlined in the summary for more in-depth details.
For the same reason, you will note that I have decided to leave out several references to man pages of LDAP tools for the sake of brevity, but the corresponding explanations are at a fingertip’s distance (man ldapadd, for example).
That said, let’s get started.
Our Testing Environment
Our test environment consists of two RHEL 7 boxes:
Server: FQDN:
Client: FQDN:
If you want, you can use the machine installed in Part 12: Automate RHEL 7 installations using Kickstart as client.

What is LDAP?

LDAP stands for Lightweight Directory Access Protocol and consists in a set of protocols that allows a client to access, over a network, centrally stored information (such as a directory of login shells, absolute paths to home directories, and other typical system user information, for example) that should be accessible from different places or available to a large number of end users (another example would be a directory of home addresses and phone numbers of all employees in a company).
Keeping such (and more) information centrally means it can be more easily maintained and accessed by everyone who has been granted permissions to use it.
The following diagram offers a simplified diagram of LDAP, and is described below in greater detail:
LDAP Diagram
LDAP Diagram
Explanation of above diagram in detail.
  1. An entry in a LDAP directory represents a single unit or information and is uniquely identified by what is called a Distinguished Name.
  2. An attribute is a piece of information associated with an entry (for example, addresses, available contact phone numbers, and email addresses).
  3. Each attribute is assigned one or more values consisting in a space-separated list. A value that is unique per entry is called a Relative Distinguished Name.
That being said, let’s proceed with the server and client installations.

Installing and Configuring a LDAP Server and Client

In RHEL 7, LDAP is implemented by OpenLDAP. To install the server and client, use the following commands, respectively:
# yum update && yum install openldap openldap-clients openldap-servers
# yum update && yum install openldap openldap-clients nss-pam-ldapd
Once the installation is complete, there are some things we look at. The following steps should be performed on the server alone, unless explicitly noted:
1. Make sure SELinux does not get in the way by enabling the following booleans persistently, both on the server and the client:
# setsebool -P allow_ypbind=0 authlogin_nsswitch_use_ldap=0
Where allow_ypbind is required for LDAP-based authentication, and authlogin_nsswitch_use_ldap may be needed by some applications.
2. Enable and start the service:
# systemctl enable slapd.service
# systemctl start slapd.service
Keep in mind that you can also disable, restart, or stop the service with systemctl as well:
# systemctl disable slapd.service
# systemctl restart slapd.service
# systemctl stop slapd.service
3. Since the slapd service runs as the ldap user (which you can verify with ps -e -o pid,uname,comm | grep slapd), such user should own the /var/lib/ldap directory in order for the server to be able to modify entries created by administrative tools that can only be run as root (more on this in a minute).
Before changing the ownership of this directory recursively, copy the sample database configuration file for slapd into it:
# cp /usr/share/openldap-servers/DB_CONFIG.example /var/lib/ldap/DB_CONFIG
# chown -R ldap:ldap /var/lib/ldap
4. Set up an OpenLDAP administrative user and assign a password:
# slappasswd
as shown in the next image:
Set LDAP Admin Password
Set LDAP Admin Password
and create an LDIF file (ldaprootpasswd.ldif) with the following contents:
dn: olcDatabase={0}config,cn=config
changetype: modify
add: olcRootPW
  1. PASSWORD is the hashed string obtained earlier.
  2. cn=config indicates global config options.
  3. olcDatabase indicates a specific database instance name and can be typically found inside /etc/openldap/slapd.d/cn=config.
Referring to the theoretical background provided earlier, the ldaprootpasswd.ldif file will add an entry to the LDAP directory. In that entry, each line represents an attribute: value pair (where dn, changetype, add, and olcRootPW are the attributes and the strings to the right of each colon are their corresponding values).
You may want to keep this in mind as we proceed further, and please note that we are using the same Common Names (cn=) throughout the rest of this article, where each step depends on the previous one.
5. Now, add the corresponding LDAP entry by specifying the URI referring to the ldap server, where only the protocol/host/port fields are allowed.
# ldapadd -H ldapi:/// -f ldaprootpasswd.ldif 
The output should be similar to:
LDAP Configuration
LDAP Configuration
and import some basic LDAP definitions from the /etc/openldap/schema directory:
# for def in cosine.ldif nis.ldif inetorgperson.ldif; do ldapadd -H ldapi:/// -f /etc/openldap/schema/$def; done
LDAP Definitions
LDAP Definitions
6. Have LDAP use your domain in its database.
Create another LDIF file, which we will call ldapdomain.ldif, with the following contents, replacing your domain (in the Domain Component dc=) and password as appropriate:
dn: olcDatabase={1}monitor,cn=config
changetype: modify
replace: olcAccess
olcAccess: {0}to * by dn.base="gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth"
  read by dn.base="cn=Manager,dc=mydomain,dc=com" read by * none

dn: olcDatabase={2}hdb,cn=config
changetype: modify
replace: olcSuffix
olcSuffix: dc=mydomain,dc=com

dn: olcDatabase={2}hdb,cn=config
changetype: modify
replace: olcRootDN
olcRootDN: cn=Manager,dc=mydomain,dc=com

dn: olcDatabase={2}hdb,cn=config
changetype: modify
add: olcRootPW

dn: olcDatabase={2}hdb,cn=config
changetype: modify
add: olcAccess
olcAccess: {0}to attrs=userPassword,shadowLastChange by
  dn="cn=Manager,dc=mydomain,dc=com" write by anonymous auth by self write by * none
olcAccess: {1}to dn.base="" by * read
olcAccess: {2}to * by dn="cn=Manager,dc=mydomain,dc=com" write by * read
Then load it as follows:
# ldapmodify -H ldapi:/// -f ldapdomain.ldif
LDAP Domain Configuration
LDAP Domain Configuration
7. Now it’s time to add some entries to our LDAP directory. Attributes and values are separated by a colon (:)in the following file, which we’ll name baseldapdomain.ldif:
dn: dc=mydomain,dc=com
objectClass: top
objectClass: dcObject
objectclass: organization
o: mydomain com
dc: mydomain

dn: cn=Manager,dc=mydomain,dc=com
objectClass: organizationalRole
cn: Manager
description: Directory Manager

dn: ou=People,dc=mydomain,dc=com
objectClass: organizationalUnit
ou: People

dn: ou=Group,dc=mydomain,dc=com
objectClass: organizationalUnit
ou: Group
Add the entries to the LDAP directory:
# ldapadd -x -D cn=Manager,dc=mydomain,dc=com -W -f baseldapdomain.ldif
Add LDAP Domain Attributes and Values
Add LDAP Domain Attributes and Values
8. Create a LDAP user called ldapuser (adduser ldapuser), then create the definitions for a LDAP group in ldapgroup.ldif.
# adduser ldapuser
# vi ldapgroup.ldif
Add following content.
dn: cn=Manager,ou=Group,dc=mydomain,dc=com
objectClass: top
objectClass: posixGroup
gidNumber: 1004
where gidNumber is the GID in /etc/group for ldapuser) and load it:
# ldapadd -x -W -D "cn=Manager,dc=mydomain,dc=com" -f ldapgroup.ldif
9. Add a LDIF file with the definitions for user ldapuser (ldapuser.ldif):
dn: uid=ldapuser,ou=People,dc=mydomain,dc=com
objectClass: top
objectClass: account
objectClass: posixAccount
objectClass: shadowAccount
cn: ldapuser
uid: ldapuser
uidNumber: 1004
gidNumber: 1004
homeDirectory: /home/ldapuser
userPassword: {SSHA}fiN0YqzbDuDI0Fpqq9UudWmjZQY28S3M
loginShell: /bin/bash
gecos: ldapuser
shadowLastChange: 0
shadowMax: 0
shadowWarning: 0
and load it:
# ldapadd -x -D cn=Manager,dc=mydomain,dc=com -W -f ldapuser.ldif
LDAP User Configuration
LDAP User Configuration
Likewise, you can delete the user entry you just created:
# ldapdelete -x -W -D cn=Manager,dc=mydomain,dc=com "uid=ldapuser,ou=People,dc=mydomain,dc=com"
10. Allow communication through the firewall:
# firewall-cmd --add-service=ldap
11. Last, but not least, enable the client to authenticate using LDAP.
To help us in this final step, we will use the authconfig utility (an interface for configuring system authentication resources).
Using the following command, the home directory for the requested user is created if it doesn’t exist after the authentication against the LDAP server succeeds:
# authconfig --enableldap --enableldapauth --ldapbasedn="dc=mydomain,dc=com" --enablemkhomedir --update
LDAP Client Configuration
LDAP Client Configuration
Feel free to leave any questions you may have using the comment form below.

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