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

How to Create a Link Aggregation – Bonding on Solaris

A link aggregation consists of several interfaces on a system that are configured together as a single, logical unit. Link aggregation, also referred to as trunking

Basically link aggregation is like a bonding on server. Its work in active and passive mode. At a time one network device are up and other bonding device are in stand by mode.

Requirements for Link Aggregations:-

1. Your link aggregation configuration is bound by the following requirements:

2. You must use the dladm command to configure aggregations.

3. An interface that has been plumbed cannot become a member of an aggregation.

4. Interfaces must be of the GLDv3 type: xge, e1000g, and bge.

5. All interfaces in the aggregation must run at the same speed and in full-duplex mode.

If the solaris box matches these above requirement, after that we can only able to create a link aggregation.

How to create a link aggregation in Solaris operating system:-

1. As a root user please login on the solaris operating system so you have full administrative role to perform the action.

2. Determine which interfaces are currently installed on your system.

For this work you need to run the below command.

#dladm show-link

The above command show you the which interfaces are currently installed on your system.

#dladm show-link

ce0             type: legacy    mtu: 1500       device: ce0

ce1             type: legacy    mtu: 1500       device: ce1

bge0            type: non-vlan  mtu: 1500       device: bge0

bge1            type: non-vlan  mtu: 1500       device: bge1

As per link aggregation requirement, we can only use the interface which start from bge etc. here the device bge0, bge1 are currently installed on the server.

3. In this step now determine which interfaces have been plumbed. for this please run the below command.

#ifconfig -a

lo0: flags=2001000322 <UP,LOOPBACK,RUNNING,MULTICAST,IPv4,VIRTUAL> mtu 8232 index 1

        inet 127.0.0.1 netmask ff000000 

ce0: flags=1000420 <UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 2

        inet 192.168.1.43 netmask ffffff00 broadcast 192.168.1.255

        ether 0:4:7c:8:92:7d 

4. Now create a link aggregation using below command

#dladm create-aggr -d bge0 -d bge1 1

here 1 is the key number which identify the link aggreation , and it is lowest number.

5. now configure & plumb the newly created aggregation. Please use the below command to do this.

#ifconfig aggr1 plumb 192.168.1.56 up

6. To check the status of the aggregation you just created, please run the below command.

#dladm show-aggr

key: 1 (0x0001) policy: L4      address: 0:4:7c:8:92:7d (auto)

device   address           speed         duplex  link    state

bge0     0:4:7c:9:87:4e    1000  Mbps    full    up      attached

bge1     0:4:7c:9:32:9e    0     Mbps    unknown down    standby

7. For link aggregations with IPv4 addresses, create an /etc/hostname.aggrkey file.

#vi /etc/hostname.aggr1

92.168.1.56

8. perform a reboot.

#reboot -- -r

How to install and configure samba server in RHEL 7 or redhat linux 7

Login on Samaba server
Check samba rpm installed or not, if not installed please install it,

[root@localhost ~]# rpm -qa | grep samba
[root@localhost ~]# yum install samba*

Create a directory in root file system which is shared with client.

[root@localhost ~]#mkdir -p /home/testuser/test

Add a new group or can use existing group

To provide access on shared directory,Here we are adding new group called samba

[root@localhost ~]#groupadd samba

Change the group and permission of sharing folder

[root@localhost ~]#chgrp -R samba /home/testuser/test
[root@localhost ~]#chmod -R 777 /home/testuser/test

create user, add into group and set samba password

[root@localhost ~]#useradd testuser
[root@localhost ~]#usermod -G samba testuser
[root@localhost ~]#smbpasswd -a testuser

Now Edit /etc/samba/smb.conf file

Note: Please take a backup of origianl file.

[root@localhost ~]#cd /etc/samba/
[root@localhost ~]#cp -p smb.conf smb.conf.orig

And add the below given contents in last line of /etc/samba/smb.conf file.

vi /etc/samba/smb.conf

[test]
comment = shared-directory
path = /home/testuser/test
public = no
valid users = testuser, @samba
writable = yes
browseable = yes
create mask = 0774
directory mask = 4774

##Edit these lines in /etc/samba/smb.conf . To allow network to reach samba server

interfaces = lo ens32 192.168.1.0/24
hosts allow = 127. 192.168.1.

security = user
passdb backend = tdbsam
netbios name = localhost
server string = Samba Server localhost
workgroup = MYGROUP
log file = /var/log/samba/samba.log
max log size = 50
security = server

Add services in /etc/services files

vi /etc/services
 
netbios-ns    137/tcp    # netbios name service
netbios-ns    137/udp    # netbios name service
netbios-dgm    138/tcp    # netbios datagram service
netbios-dgm    138/udp    # netbios datagram service
netbios-ssn    139/tcp    # netbios session service
netbios-ssn    139/udp    # netbios session service

Note: Please check these above ports are open from this samba server to client machine

Now start the smb and nmb services.

systemctl start smb.service
systemctl start nmb.service

Enable smb and nmb service at booting of system

systemctl enable smb.service
systemctl enable nmb.service

Note 1: firewalld service not enable on this server so no need to add any rule.
Note 2: selinux is in permissive state so no need to change the selinux security context.

Now login on window machine

and mount this samba share on the server.

\\localhost.redhat.com\test

How to Create VNIC and Assign a IP Address on Solaris 11

For creating Virtual NIC and assigning fix static IP address in Solaris 11 we need to understand the basic difference between older version of Solaris and Solaris 11.

In Solaris 10, according to the NIC manufacturer,physical network interfaces are named as (Ex:bge,e1000g,nxge).But in Solaris 11 onwards,the names are hidden from the view and all the interfaces will be named as net0,net1…netx.

Before forward to main work we need to know that using which command we can check which interface has been mapped to physical interface. Using below command you can check all the network interface details.

sun01# dladm show-phys

LINK              MEDIA                STATE      SPEED  DUPLEX    DEVICE

net0              Ethernet             up         1000   full      bge001

net1              Ethernet             up         1000   full      bge002

If you want to show all dladm level devices,including VNIC’s & aggregation links,use the below command-

sun01# dladm show-link

LINK                CLASS     MTU    STATE    OVER

net0                phys      1500   up       --

net1                phys      1500   up       --

In Solaris 11,you can give a meaning full description(net1/oracle_VIP) to all the IP address on the system unlike Solaris 10. (e1000g1:2)

How to assigning new IP address to NIC:-

1. We can see how we assigned IP address to the physical interface, so in the first step we will check all the physical interface using below command.

sun01# dladm show-phys

LINK              MEDIA                STATE      SPEED  DUPLEX    DEVICE

net0              Ethernet             up         1000   full      bge001

net1              Ethernet             up         1000   full      bge002

2. In this step we would know how we will create a new interface so you can use the below command for this.

sun01# ipadm create-ip net1

3. This is the main step to assign the static ip address to the newly created interface net1. You can use below command or syntax to assign the fixed IP.

sun01#ipadm create-addr -T static -a local=10.135.0.2/24 net1

You can change your IP address accordingly. 

4. Now we will Verify whether IP address is configured or not which we assigned on above step.

sun01# ifconfig  net1

net1: flags=1000843 mtu 1500 index 7

        inet 10.135.0.2 netmask ffffff00 broadcast 10.135.0.255

        ether 0a:cB:12:8e:15:e2

If you see the above output, the new IP address is shown on net1 interface successfully. Using above all 4 steps you can know how we will assinged the static ip address to the sun solaris 11 operating system.

Now we will go for Virtual Network Interface creation steps.I can create N number of VNIC’s using single physical interface.These VNIC are treated as actual physical interface and possible to assign to local zones with  full access to it.

How to create a new VNIC using interface net2:-

1. In the initial steps I will run the same command to check out the all physical interface which is available on the Solaris 11 Server.

sun01# dladm show-phys

LINK              MEDIA                STATE      SPEED  DUPLEX    DEVICE

net0              Ethernet             up         1000   full      bge001

net1              Ethernet             up         1000   full      bge002

net2              Ethernet             unknown    1000   full      bge003

If you see the above command output network interface "net2" is in unknow state, So in the next step I will create a new VNIC using net2.

2. In this step we will create a new VNIC using net2. In my case i will suppose VNIC name “vnic01”, so for creating the new VNIC we will run the below command which describe below.

sun01#dladm create-vnic  -l net2 vnic01

3.Now, We will plumb the virtual interface and create a default IP to new VNIC.

sun01# dladm create-vnic  -l net2 vnic01

sun01# ipadm create-ip vnic01

sun01# ifconfig vnic01

vnic01: flags=1000842 mtu 1500 index 8

        inet 0.0.0.0 netmask 0

        ether 2c:18:10:Ce:1a:12

4. Now we will assign the new IP address to VNIC and verfif that new IP for vnic01 is configured or not.

sun01# ipadm create-addr -T static -a local=10.135.0.3/24 vnic01

sun01# ifconfig vnic01

vnic01: flags=1000843 mtu 1500 index 8

        inet 10.135.0.3 netmask ffffff00 broadcast 10.135.0.255

        ether 2c:18:10:Ce:1a:12

5. In the final step we will try to run snoop on VNIC which we have create now. You can verify through snooping is that VNIC01 is working fine or not.

sun01# snoop -d vnic01

The same way you can create a multiple VNIC and assign a new IP address to it. Hope you got some idea about Solaris 11 networking part after reading this post. Please let me know if you have any doubt regarding this post.