SSH or SFTP Authentication issue in linux

We normally getting a below error while accessing the destination server via SSH or SFTP protocols.

Error:

root@localhost> sftp  root@XYZ.com

warning: Authentication failed.

FATAL: ssh2 client failed to authenticate. (or you have too old ssh2 installed, check with ssh2 "-V")

To resolve this error first we need to understand what is an issue. In such type of above error, issue is mostly from destination server end which you want to connect from your system. 

In /etc/ssh/sshd_config file, a parameter "MaxAuth Tries" value is very less due to this when we are attempting to access the destination server using SSH or SFTP protocol then we will get such issue if your account will not authenticate in first two attempts. 

So to resolve such issue , you need to increase the value of "MaxAuth Tries" from default value.

edit the /etc/ssh/sshd_config file

search this parameter

increase the value "MaxAuth Tries" to "5" and take a restart of ssh service

systemctl restart sshd

login on source server again and try to access the server, if you are facing this issue again then increase the value again and set to 20.

Zoning in Brocade FC SAN switch

SAN zoning is a method to manages communication of hosts and storage nodes.

Each device in a Fiber Channel will have a unique Word Wide Name (WWN). Zone contains WWN name of these devices.

There are two types of WWNs:

Word Wide Node Name (WWNN)
Word Wide Port Name (WWPN)

We can identify devices in FC using WWNN or WWPN. The idea is to bind WWPN’s of intended devices (ports) together.

This binding is called zoning and it manages communication of hosts and storage nodes.
 

SAN Zoning Method:
 

Please run the "switchshow" command. This command will help you to identify the HBA address of both the target and initiator ports which will be required for SAN Zoning configuration.

Output of this command will provide below output.

barcode01:admin> switchshow
switchName:     barcode01
switchType:      71.2
switchState:      Online
switchMode:     Native
switchRole:      Subordinate
switchDomain: 101
switchId:          fffc65
switchWwn:     90:XX:XX:99:XX:XX:ef:XX
zoning:             ON (fabric_A)
switchBeacon: OFF

Index Port Address Media Speed State     Proto
==============================================
   0   0   650000   --     N8   No_Module   FC
   1   1   650100   id     N8   Online      FC  F-Port  90:XX:XX:99:XX:XX:cf:XX
   2   2   650200   id     N8   No_Light    FC
   3   3   650300   id     N8   Online      FC  E-Port  90:01:c4:f5:7c:e7:3e:23
   4   4   650400   id     N8   Online      FC  F-Port  90:00:02:e0:db:1e:f6:10
   5   5   650500   id     N8   Online      FC  F-Port  90:00:00:e0:db:1e:f6:10
   6   6   650600   id     N8   Online      FC  F-Port  90:01:43:80:21:df:7a:12
   7   7   650700   id     N8   Online      FC  F-Port  90:01:43:80:21:df:78:16
   8   8   650800   id     N8   Online      FC  F-Port  91:02:00:02:ac:01:eb:11
   9   9   650900   id     N8   Online      FC  E-Port  90:00:50:eb:1a:ed:21:10
 
 
The 90:XX:XX:99:XX:XX:cf:XX is the WWPN of the device connecting in that port. We will use this WWPN of the connecting device to zone with another.

In below step we will create a new alias for above WWPN number as it is very difficult to remember this WWPN number during zoning.

barcode01:admin> alicreate hostname_port1,"90:XX:XX:99:XX:XX:cf:XX"

To verify run command, alishow “hostname_port1”.

Now we are going to create two zones with two aliases.

barcode01:admin> zonecreate zone01,'hostname_port1;storage_port01'

To verify run command, zoneshow “zone01”.

Once zone is created, add it to an active configuration or a new configuration by running either the cfgadd command or cfgcreate.

barcode01:admin> cfgadd fabric_A,zone01

If zone configuration not exist then please run the below command to create a zone configuration which will consist zones that we have created recently.

barcode01:admin> cfgcreate "fabric_A", "zone01"

In my case I have already created this. above is just an example to create a zone configuration if not exist.

Next you have to save the configuration by running the cfgsave And it will prompt for yes / no  you have to hit  yes at the prompt to save the configuration.

barcode01:admin> cfgsave

WARNING!!!
The changes you are attempting to save will render the
Effective configuration and the Defined configuration
inconsistent. The inconsistency will result in different
Effective Zoning configurations for switches in the fabric if
a zone merge or HA failover happens. To avoid inconsistency
it is recommended to commit the configurations using the
'cfgenable' command.

Do you want to proceed with saving the Defined
zoning configuration only?  (yes, y, no, n): [no] y
Updating flash ...

To activate the created zoning, run the cfgenable And it will prompt for yes / no, you have to hit yes at the prompt to activate the configuration.

barcode01:admin> cfgenable fabric_A

You are about to enable a new zoning configuration.
This action will replace the old zoning configuration with the
current configuration selected. If the update includes changes
to one or more traffic isolation zones, the update may result in
localized disruption to traffic on ports associated with
the traffic isolation zone changes
Do you want to enable 'fabric_A' configuration  (yes, y, no, n): [no] y
zone config "fabric_A" is in effect
Updating flash ...

barcode01:admin>

Note: This will put the zone into the Effective Configuration and will be live in production.

Hope reading above article you can perform SAN zoning without any issue. In case of any query, please comment in below section. Thanks!!

How to reset HP iLO password from command line in Linux

If you have lost or forgotten the iLO password than please find the below steps to reset ilo password from command line.

To reset / set the password of the iLO from within the linux operating system on an HP server, the hponcfg utility needs to be installed

Here is some information about hponcfg - 

The hponcfg utility is an online configuration tool used to set up and reconfigure the local iLO without requiring a reboot of the server operating system. It can be used to retrieve and change the iLO configuration of the local server from the linux command line.

Please login on the linux machine and create a new xml file

[root@localhost]#vim ilo_password.xml

<RIBCL VERSION="2.0">

  <LOGIN USER_LOGIN="x" PASSWORD="x">

  <USER_INFO MODE="write">

    <MOD_USER USER_LOGIN="Administrator">

      <PASSWORD value="XXXXXXXX*"/>

    </MOD_USER>

  </USER_INFO>

  </LOGIN>

</RIBCL>

save the ilo_password.xml file

In above xml file, you just need to set PASSWORD value - XXXXXXX. Please put your new ILO password here. 

To load this xml file in ILO, please use hponcfg command 

[root@localhost]# hponcfg -w ilo_password.xml

Your iLO password will be reset, now please login in HPE iLO via new password XXXXXXX.

Please let me know in case of any query about this post. Thanks. 

Failed to start lsb bring up/down networking in rhel 7

Such type of error we have received after operating system upgradation from redhat linux operating system from version 7.x to version 7.y.

The root cause for error is network manager upgradation during operating system patching.

To troubleshoot this error, please restart the network service and check the status 

[root@localhost network-scripts]# systemctl restart network

Job for network.service failed because the control process exited with error code. See "systemctl status network.service" and "journalctl -xe" for details.

[root@localhost network-scripts]# systemctl status network

You can see " Failed to start lsb bring up/down networking" error message

Solution: To resolve such type of network issue, please perform the below steps.

Go to /etc/sysconfig/network-scripts/ directory and list the files.

[root@localhost]# cd /etc/sysconfig/network-scripts/

You can see the ifcfg-lo filename file which you need to removed it.

after remove this file please take a restart of service. Your network service will restart properly without any issue. Also if you have any other duplicate or backup ifcfg file please remove it.

[root@localhost network-scripts]# rm -rf ifcfg-lo

[root@localhost network-scripts]# systemctl restart network

Now try to access the redhat machine via ssh. Please post your comment if you have any query regarding this post. 

NFS Stale File Handle error and solution

In linux machine we have NFS mounted directories sometimes contain stale file handles. If you run command such as ls or vi you will see an error

# ls

.: Stale File Handle

Before moving to fix this issue first we need to understand the concept of Stale File Handle.

A filehandle becomes stale whenever the file or directory referenced by the handle is removed by another host.

while your client still holds an active reference to the object. A typical example occurs when the current directory of a process, running on your client, is removed on the server (either by a process running on the server or on another client).

So this can occur if the directory is modified on the NFS server, but the directories modification time is not updated.

To fixed this issue, the best solution is to remount directory from the NFS client using mount command.

# umount -f /test

# mount -t nfs nfsserver:/path/to/share /test

How can I mount a read-only filesystem as read-write in redhat linux

This post is related to the below issue which you have faced in Red Hat Linux 5/6 operating system.

Issue :
 

➤ One of my partition has been mounted as read-only. How can I make it read-write without rebooting?

➤ How can I remount the root filesystem as read-write after it goes read-only?

➤ My filesystem went read-only, can I remount without rebooting? / filesystem suddenly became read only, unable to write to files.

➤ Also if you are trying to create any file or directory inside the file system you would get the message- "Read only file system"

 [root@localhost]# touch test
touch: cannot touch `test': Read-only file system

 [root@localhost]# cat /proc/mounts
rootfs / rootfs rw 0 0
/dev/root / ext3 ro,data=ordered 0 0

Solution:

Mount an already mounted file system in read-write option, Please run the below command.

 [root@localhost]# mount -o remount,rw <filesystem_path>

Remounting as read-write may work, however, if the file system remounts as read-only again, a filesystem check and reboot of the system will be required.

How to configure Network Bonding on RHEL 7

Step by Step method to configure the network bonding on RHEL 7:

 

➤ Please log on to linux server and run the "ip a" command to check the available interfaces.

    [root@localhost]# ip a
    lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever

    eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000
    link/ether 00:50:56:bd:c7:f9 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.2 brd 192.168.1.255 scope global eth0
       valid_lft forever preferred_lft forever

➤ Load the bonding driver called “bonding” in the kernel with the modprobe command if it is not already loaded, and verify with the modinfo command:

[root@localhost]# modprobe bonding
[root@localhost]# modinfo bonding
 

➤ In this step you need to generate UUIDs for interfaces using the below command.

[root@localhost]# uuidgen <interface-name>
 

➤ Now create a file called ifcfg-bond0 in the /etc/sysconfig/network-scripts directory for bond0 with the following settings. Please use vi editor to edit this file.

[root@localhost]# cd /etc/sysconfig/network-scripts
[root@localhost]# vi ifcfg-bond0

DEVICE=bond0
Name=bond0
TYPE=bond0
BONDING_MASTER=yes
BONDING_OPTS="mode=balance-rr"
ONBOOT=yes
IPADDR=192.168.1.23
NETMASK=255.255.255.0
GATEWAY=192.168.1.1
 

➤ Now create ifcfg-eth2 and ifcfg-eth3 files in the /etc/sysconfig/network-scripts directory for eth2 and eth3 interfaces with the following settings. Set the MASTER directive to bond0. Both interfaces will act as slaves with no IP addresses assigned to them.

[root@localhost]# vi ifcfg-eth1

DEVICE=eth1
TYPE=Ethernet
NAME=eth1
UUID=23a32d65-343d-48a2-8rf7-d2jh2388f666
ONBOOT=yes
MASTER=bond0
SLAVE=yes

[root@localhost]# vi ifcfg-eth2

DEVICE=eth2
TYPE=Ethernet
NAME=eth2
UUID=22a32d65-443d-48d2-8rf7-d2jh222f666
ONBOOT=yes
MASTER=bond0
SLAVE=yes
 

➤ Now deactivate and reactivate bond0 with the ifdown and ifup commands:

[root@localhost]# ifdown bond0; ifup bond0
 

➤ Check the status of bond0 and the slaves with the ip command. It should also show the assigned IP.

[root@localhost]# ip addr
 

➤ Restart the system to ensure the configuration survives system reboots
[root@localhost]# reboot