3. Redhat Linux : RHCE 6
Giving sudo privilage to users:
------------------------------
1. edit /etc/sudoers using 'visudo -f /etc/sudoers' command
Line 21 : User_Alias GROUP_NAME = User_name1, User_name2, ...
Line 37 : Cmnd_Alias CMD = /usr/sbin/command, ...
Line 38 : GROUP_NAME ALL = CMD
* By doing this, the users in the group will get the previlage to do the specified commands.
2. edit /etc/sudoers using 'visudo -f /etc/sudoers' command
add '%groupname ALL=(ALL) ALL'
* This will give complete root permission for all the group members.
Filesystem:
----------
* ext4 is used rhel6
* IDE will be listed as /dev/hda
* Other devoces like sata, ata, scsi will be listed as /dev/sda
* FS types:
Disk based : ext4, NTFS
Pseuodo based : swap
Network based : NFS
* IBM PC Rule:
Only 4 primary partitions are possible in any harddsiks.
So first 3 will be as primary and next will be made extended for more number of partitions.
Extended partitons can be from sda5-sda15
These are called as logical partitions
* Partition IDs:
Swap : 82
Extended : 83
LVM : 8e
* fields in /etc/fstab:
/dev/sdb5(device) mountpoint(/mnt) filesystem_type(ext4) user_permissions(defaults) dump(0,1) fsck(0,1)
* update these for permenant mounting
eg:- Delete swap area and resize it
1. fdisk /dev/sda
p
d
'n'
w
n
default starting cylinder
+3G
w
2. fdisk /dev/sdx
t
'n'
82
w
3. mkswap /dev/sdx
4. vim /etc/fstab
add : /dev/sdax swap swap defaults 0 0
5. partprobe /dev/sdx
6. reboot
Encrypting the harddisk with LUKS:
---------------------------------
* Linux Unified Key Setup is to setup password security for harddisk drives.
* edit in /etc/crypttab
name /dev/sdx
* edit in /etc/fstab(not sure, trainer not explained)
* cryptsetup luksOpen dev/sdx name
* cryptsetup luksClose name
# /* MAKE THE PARTITION IN LINUX LVM FORMAT */
Logical Volume Manager
----------------------
* flexible storage
* hard disks form physical volumes which forms Volume groups which can create logical volumes
* max no of PVs possible is 256 to form a VG
* max no of LVs from a VG is 256
1. Creating a Physical Volume:
-----------------------------
* create some free partitons, say /dev/sdax, /dev/sday
* make the partition types as Linux LVM(8e)
fdisk /dev/sdx
select the partition
type 't'
type '8e'
Do it for all PV partitions
* pvcreate /dev/sdax /dev/sday ....
2. Creating a Volume group:
--------------------------
* vgcreate vg_name /dev/sdax /dev/sday ....
* vgdisplay vg_name
* vgcreate -s 8 vg_name /dev/sdx /*Create a VG with PE=8M(Physical Extend or Physical Partition)*/
3. Extending a VG:
-----------------
* pvcreate /dev/sdax /*Create a new Linux LVM partition(PV) to add to vg*/
* vgextend vg_name /dev/sdax
4. Creating a Logical Volume:
----------------------------
* lvcreate -n lv_name -l 20 vg_name
* lvdisplay /dev/vg_name/lv_name
* mkfs.ext4 /dev/vg_name/lv_name
* mount /dev/vg_name/lv_name /mount_point
5. Extending an LV:
------------------
* lvextend -L +100M /dev/vg_name/lv_name
* lvextend -l +5 /dev/vg_name/lv_name
* resize2fs -p /dev/vg_name/lv_name
6. Reducing an LV:
------------------
* umount /mount_point
* e2fsck -f /dev/vg_name/lv_name
* resize2fs -p /dev/vg_name/lv_name 'n'M
* lvreduce -l -10 /dev/vg_name/lv_name
7. Reducing a VG:
----------------
* vgreduce vg_name /dev/sdax /*Remove a PV from VG*/
8. Removing LV:
--------------
* lvremove /dev/vg_name/lv_name
9. Removing VG:
--------------
* vgremove vg_name
10. Removing PV:
---------------
* pvremove /dev/sdx /dev/sdy /dev/sdz
11. To list PV, VG and LV:
-------------------------
* pvs
* vgs
* lvs
/*
Commands for the day:
--------------------
* free -m : to see the free spaces in swap
* mkswap /dev/sdax : to create swap
* swapon /dev/sdax : mount swap temporarily
* swapoff /dev/sdax : unmount swap
* fdisk /dev/sda : to edit partitons
* partprobe /dev/sda : command for re-reading the partition table
* lvremove /dev/VG1/LV1
* df -hT
* vgremove VG1
* pvremove /dev/sda7 /dev/sda8 /dev/sda9
* pvs
* vgs
* lvs
*/
