11-22-2020

https://youtu.be/bs0FE_VAUvs

 

 

Emergency Mode

 

 

 

 

-          The system boot to emergency mode. But why?

a.       Missing drives

b.       The file system is corrupted

c.       The file system is  unmountable

-          During boot process /etc/fstab read by system

-          This will halt the system going into default mode

 

 

-          Enter password

-          Edit /etc/fstab

-          Comment out the missing disks

 

 

 

 

Filesystem

Mount point

Filesystem type

OS handles this

Priority – 0 1 or 2

/dev/sdb1

/DATA                       

ext4

defaults

  0 0

 

 

 

 

 

File System Check

0

skip

1

1 higher priority

2

2 lesser priority

 

 

For demo purpose lests corrupt file system – triggring

 

[root@zmpt01 ~]# dd if=/dev/zero of=/dev/sdd1 bs=1k count=1024   < ---corrupted on block size

1024+0 records in

1024+0 records out

1048576 bytes (1.0 MB) copied, 0.00584049 s, 180 MB/s

 

System will halt and goes into emergency mode

 

Emergency mode is in Read Only mode

 

mount –o remount, rw /    #< --- Command to load system in read/ write mode, so you can edit /etc/fstab

 

Putty is disabled – because Emergency mode is without network

 

 

Run mount –a

 

 

 

xfs_repair /dev/sdd1              #< ----run this command to repair in real world scenerio

 

90% successful – Quaratine the bad sectors

 

For ext4

 

fsck /dev/sdd1

 

fsck – file system check