linux guide

If we have logical volume we can dynamicly add or remove diskspace to or from it. Any disk partitions to used as physical volumes need to have their partition types set to 8e, Linux LVM. After creating Primary Volu me, we must create a Volume Group with any name.After that we will create Logical Volume. Not only to the Logical Volume, we can extend or reduce the size of a Volume Group.
Lets start -
Create a Partition of LVM type using fdisk and reboot the system. –

fdisk /dev/hda
n
(define/accept the first cylinder)
(define the last cylinder) +100M
n
(define/accept the first cylinder)
(define the last cylinder) +150M
p (check the newly created partitions at the bottom, note down the partition no.
We are assuming /dev/hda10 and /dev/hda11 are created)
t
10 (partition no)
l ( to list codes - please note the code for Linux LVM, it is 8e)
8e
t
11 (partition no)
8e
w ( to write to partition table and exit from fdisk)

reboot ( reboot your system)

Initialize the LVM Configuration Files
vgscan

Initialize the LVM partitions as physical volumes.
pvcreate /dev/hda10 /dev/hda11

Create Vouume Group.
vgcreate vg1 /dev/ hda10
Here, vg1 is volume group name

Create Logical Volume.

lvcreate -L 50M -n lvm1 vg1
Here, lvm1 is logical volume name

Make filesystem.

mkfs /dev/vg1/lvm1
Mount the newly created logical volume to a directory, say /lvmone
mount /dev/vg1/lvm1 /lvmone

Check the volume size.

lvdisplay /dev/vg1/lvm1


If you want to resize it, first unmount the partion and run
e2fsadm -L+25M /dev/vg1/lvm1

Check the volume size once again. If you want to reduce the partition size run -
e2fsadm -L-20M /dev/vg1/lvm1

Run the following command to see the volume group size and space left on it.
vgdisplay

To extend the volume group size

vgextend vg1 /dev/hda11

Run ‘vgdisplay’ once again to check the volume group size, allocated space and free space.

Labels: command, configuration, edit, file system, guide to linux, instalation, Linux, linux administrator guide, linux config, lvm.LOGICAL VOLUME MANAGER, pocket linux guide, red hat linux guide

To Change owner of a file
chown user_name file_name
Example: You want to make gautam as owner of beragautam.tx
chown gautam beragautam.tx

To change owner and group of a file
chown user_name.group_name file_name

You can also use this command as follows –
chown user_nam:group_name file_name
(Please note, you can use either “:” or “.”)

If you want to assign a file would be used by a group use the following command.
chgrp special atanu.tx
Here group name is special and file name is beragautam.tx

What is a group?
A group is used to represent users, who have similar characteristics,exercise similar tasks and
enjoy similar permission and environment in a network. Now think about the situation here.
You have a group of users who need similar type of access to a file, beragautam.tx. What you will do? Very simple

Create a group.

Issue the command that enables the group to access the file

Give file access permission to this group. (Example, all permissions to owner and read and
execute permissions to group)

Make the users members of a group.

Do these tasks as defined below.
groupadd newgroup
chgrp newgroup bera.tx
chmod 750 beragautam.tx

And then add the user to this group.

vi /etc/group
At the bottom of the file verify the entry related to newgroup and add the user name. It
will look like –
newgroup:x:600:beragautam,gautam

Here, beragautam and gautam are members of the newly created group, ‘newgroup’. The thing
must be noted is, usernames are specified by comma (,) separated form. However,
instead of editing th e /etc/group file directly, we can use commands to add or remove
users from a group.

If we want to add members (in our example, the name of the group is acct and the
members are red and green), we can use the following command –
gpasswd –M red,green acct

If we want to add user ‘blue’ in the ‘acct’ group we can use the following command –
gpasswd –a blue acct

To remove user red from the acct group, we can use the following command –
gpasswd –d red acct

Labels: command, configuration, edit, file system, guide to linux, job, kernel, Linux, linux administrator guide, linux config, Linux installation guide, pocket linux guide, red hat linux guide