NTP Parameters

node1:/var/log # ntpdc -p (uses sec instead of ms).

     remote           local      st poll reach  delay   offset    disp
=======================================================================
=LOCAL(0)        127.0.0.1       10   64  377 0.00000  0.000000 0.03053
*circle.net          16.88.11.29   2  512  377 0.06363 -0.017075 0.11371
=netservice       16.88.11.29  16 1024    0 0.00000  0.000000 3.99217
=ntp1.iso           16.88.11.29   3  512  377 0.11404 -0.010279 0.10500
node1:/var/log #

“+” – Good and a preferred remote peer or server (included by the combine algorithm)

“*” – The remote peer or server presently used as the primary reference;

poll : NTP polls each peer every “poll” seconds.

when : is relative time of last poll.

reach : track of last successful polls, 377 is best.

Delay : is network delay, this is fine

offset : offset between local and peer clock (ms) and it should be low.

jitter : Mean deviation (jitter) in the time reported for that remote peer or server.

How to configure NTP Server In Linux

Configured NTP Server in 192.168.100.22

#Server Side
============
NTP Server Pool Address
1.server 1.asia.pool.ntp.org
2.server 0.asia.pool.ntp.org

#Permitting local network to use this
restrict 192.168.100.0 mask 255.255.255.0 nomodify notrap
restrict 192.168.10.0 mask 255.255.255.0 nomodify notrap
restrict 192.168.20.0 mask 255.255.255.0 nomodify notrap
restrict 192.168.30.0 mask 255.255.255.0 nomodify notrap
restrict 192.168.40.0 mask 255.255.255.0 nomodify notrap

#full access to the local net
restrict 127.0.0.1

#Client Side
===========

#yum install ntp

edit the ntp.conf file
#vim /etc/ntp.conf

#comment the following lines
#server 0.centos.pool.ntp.org
#server 1.centos.pool.ntp.org
#server 2.centos.pool.ntp.org

#add the following lines
restrict default ignore
server 192.168.100.22
restrict 192.168.100.1 mask 255.255.255.255 nomodify notrap noquery

#save and quit the file.

#Before starting the ntp daemon, run the following command

#ntpdate -b 192.168.100.223

#service ntpd start

#check the ntp

[root@node1 ~]# ntpq -pn
remote refid st t when poll reach delay offset jitter
==============================================================================
192.168.100.223 140.109.1.4 11 u 3 64 1 0.257 0.368 0.001
127.127.1.0 .LOCL. 10 l 2 64 1 0.000 0.000 0.001
[root@node1 ~]#

/dev/sdb: read failed after 0 of 4096 at 0: Input/output error

When a storage unit is longer available to the Linux Server, You would see the following error message:

[root@node1 /]# pvs
  /dev/sdb: read failed after 0 of 4096 at 0: Input/output error
  /dev/sdb: read failed after 0 of 4096 at 2147418112: Input/output error
  /dev/sdb: read failed after 0 of 4096 at 2147475456: Input/output error
  /dev/sdb: read failed after 0 of 4096 at 4096: Input/output error
  PV                VG       Fmt  Attr PSize  PFree
  /dev/mapper/disk1          lvm2 a--   1.00g 1.00g
  /dev/mapper/disk2          lvm2 a--   1.00g 1.00g
  /dev/mapper/disk3          lvm2 a--   1.00g 1.00g
  /dev/sda2         vg_node1 lvm2 a--  19.51g    0
[root@node1 /]#

To fix the issue, We need to delete the corresponding /dev/sdb file from OS Level.

[root@node1 /]# echo 1 > /sys/block/sdb/device/delete

[root@node1 /]# pvs
  PV                VG       Fmt  Attr PSize  PFree
  /dev/mapper/disk1          lvm2 a--   1.00g 1.00g
  /dev/mapper/disk2          lvm2 a--   1.00g 1.00g
  /dev/mapper/disk3          lvm2 a--   1.00g 1.00g
  /dev/sda2         vg_node1 lvm2 a--  19.51g    0
[root@node1 /]#

VxVM vxdisk ERROR V-5-1-684 IPC failure: Configuration daemon is not accessible

[root@node2 yum.repos.d]# cd /

[root@node2 /]# vxdisk list
VxVM vxdisk ERROR V-5-1-684 IPC failure: Configuration daemon is not accessible

[root@node2 /]# cd /etc/vx/reconfig.d/state.d/

[root@node2 state.d]# ls -l | grep -i install-db

-rw-r--r--. 1 root root 0 Sep  1 06:21 install-db

[root@node2 state.d]# rm -rf install-db

[root@node2 state.d]# vxconfigd

[root@node2 state.d]# vxdctl init

[root@node2 state.d]# vxdctl enable

[root@node2 state.d]# vxdisk list
DEVICE       TYPE            DISK         GROUP        STATUS
disk_0       auto:none       -            -            online invalid
sda          auto:LVM        -            -            online invalid
[root@node2 state.d]#