Tuesday, 10 July 2012

Unix/Linux System Admin Interview Questions And Answers 5

Q: - How you will check on Your server or system device-mapper is installed or not?

Check the following file.
#cat /proc/misc
if this file contains "device-mapper" term it means device mapper is installed on your system.
Q: - How are snapshots in LVM2 different from LVM1?

In LVM2 snapshots are read/write by default, whereas in LVM1, snapshots were read only.
Q: - What is the maximum size of a single LV?

For 2.4 based kernels, the maximum LV size is 2TB.
For 32-bit CPUs on 2.6 kernels, the maximum LV size is 16TB.
For 64-bit CPUs on 2.6 kernels, the maximum LV size is 8EB.
Q: - If a volume group named as VG0 already exists but i need to extend this volume group up to 4GB.Explain all steps?

Firstly create Physical volume (/dev/sda7) of size 4GB.
Now run following command.

vgextend VG0 /dev/sda7
but i want to remove /dev/sda7 pv from this VG0?

vgreduce VG0 /dev/sda7
Q: - Which command is used to extend a logical volume?

lvextend --size +<addsize> /dev/<vgname>/<lvname>
resize2fs /dev/<vgname>/<lvname>
Q: - Tell me all steps to remove a LVM?

To remove a logical volume from a volume group, first unmount it with the umount command:
umount /dev/<vgname>/<lvname>
and then use the lvremove command:
lvremove /dev/<vgname>/<lvname>
Q: - Which command is used to create LVM Snapshot?

vcreate --size <size> -s -n <snapshotname> <lvname>
The lvcreate command is used to create a new logical volume, meaning there must be
free physical extents in the logical volume group to create a snapshot. The -s option
means that the LV is a snapshot, <snapshotname> is the name of the new LV created, and
<lvname> is the name of the LV from which to create the snapshot.
Q: - Is there any relation between modprobe.conf file and network devices?

Yes, This file assigns a kernel module to each network device.
For Example :-
[root@localhost ~]# cat /etc/modprobe.conf
alias eth0 b44
Here b44 is the kernel module for network device eth0.
We can Confirm by following command (This module “b44” is present or not).
[root@localhost ~]# lsmod |grep b44
b44                    29005    0
Q: - What is the location of "network" file and what does this contains?

location :-  /etc/sysconfig/network
This file contains following fields
Q: - What is the role of /etc/resolv.conf file?

In this file we sets the DNS servers (using their IP addresses) and the search domain. The values of the DNS servers are often added when the network is activated because the data can be provided by DHCP or a similar service.
Q: - Which deamon is required to start Network services?

/etc/init.d/network start

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