Fwd: TechQue

1. server 1 is pingable from my desktop , but its not pingable from other server , what is the problem.
Check the IPtables on that destination server

2.how to downgrade patch if its installed with RPM and if its installed with yum
# yum downgrade package
# yum downgrade sqlite

3.Server is not pingale and found hung state in console , what can be done.

Login to console and try to see run level # who -r and try to start in MultiUser mode runlevel 5
 

4.Server is not pingable and in console its stopped in grub , what can be done.

--> you'll boot Linux from an installation CD or other 'rescue media'--->mount the system's root partition onto /mnt, then the file you would normally see as /etc/fstab will be seen as /mnt/etc/fstab. fix if there is any issue with fstab and reboot
----> if it is corrupted bcas you have 2 different Linux release on the same boot disk then do as follows.
But try remember why it was stuck at Grub, what happened before that...it all depends on that

$ sudo /mnt/usr/sbin/grub

grub> root (hd0,0)
grub> setup (hd0) (hd0,0)
 Checking if "/boot/grub/stage1" exists... yes
 Checking if "/boot/grub/stage2" exists... yes
 Checking if "/boot/grub/e2fs_stage1_5" exists... yes
 Running "embed /boot/grub/e2fs_stage1_5 (hd0)"... 15 sectors are embedded. succeeded
 Running "install /boot/grub/stage1 (hd0) (hd0)1+15 p (hd0,0)/boot/grub/stage2 /boot/grub/menu.lst"... succeeded
Done.
grub> quit

The key command here is setup (hd0) (hd0,0) which tells Grub to re-install the original stage 1 into the MBR of (hd0), and copies the original (Linux img) stage 1.5 into the sectors immediately following. (For a more detailed description of this, look up the install and embed commands in the GNU manual at www.gnu.org/software/grub/manual/grub.html) Once this is done, you can simply reboot
 

5. How to save LVM in case of drive failure
...

You may be able to find the UUID for the physical volume that was overwritten by looking in the /etc/lvm/archive directory. Look in the file VolumeGroupName_xxxx.vg for the last known valid archived LVM metadata for that volume group.

/etc/lvm/backup
# vgcfgbackup vg00(vgname)

# lvs -a -o +devices
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  Couldn't find all physical volumes for volume group VG.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  Couldn't find all physical volumes for volume group VG.
# vgchange -an --partial
  Partial mode. Incomplete volume groups will be activated read-only.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  Couldn't find device with uuid 'FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk'.
  ...
# pvcreate --uuid "FmGRh3-zhok-iVI8-7qTD-S5BI-MAEN-NYM5Sk" --restorefile /etc/lvm/archive/VG_00050.vg /dev/sdh1
  Physical volume "/dev/sdh1" successfully created

# vgcfgrestore VG
  Restored volume group VG

# lvs -a -o +devices
  LV     VG   Attr   LSize   Origin Snap%  Move Log Copy%  Devices
  stripe VG   -wi--- 300.00G                               /dev/sdh1 (0),/dev/sda1(0)
  stripe VG   -wi--- 300.00G                               /dev/sdh1 (34728),/dev/sdb1(0)

# lvchange -ay /dev/VG/stripe
[root@link-07 backup]# lvs -a -o +devices
  LV     VG   Attr   LSize   Origin Snap%  Move Log Copy%  Devices
  stripe VG   -wi-a- 300.00G                               /dev/sdh1 (0),/dev/sda1(0)
  stripe VG   -wi-a- 300.00G                               /dev/sdh1 (34728),/dev/sdb1(0)
 

6. How to retrieve data from vmx. file in case VM get corrupted
From the VMware vsphere or VMware player follow the same steps as creating a new VM and choose the VMX file when it will ask you to.