Troubleshooting

############ TROUBLESHOOTING. ###############

QUE 1) :- RECOVER ROOT PASSWORD.

1)Root password troubleshooting.

A)To lock the root user.
#usermod -L root

*To check the shadow file.
#vim /etc/shadow
root:!$1$aFq8TCs5$3kaiGxWtCSTNIt7RvQFRP0:14218:0:99999:7:::

A)ANS :-To unlock the root user.
#usermod -U root
root:$1$aFq8TCs5$3kaiGxWtCSTNIt7RvQFRP0:14218:0:99999:7:::

#head -1 /etc/shadow
root:$1$aFq8TCs5$3kaiGxWtCSTNIt7RvQFRP0:14218:0:99999:7:::
last 2 field should be empty.

#chage -l root
Password expires                                        : never
Password inactive                                       : never
Account expires                                         : never
this 3 should be never.



B)*password is not set hence no login.
#vim /etc/shadow
root:!!:14218:0:99999:7:::

ANS:- to set password.
#passwd

#vim /etc/shadow
root:$1$23urSrMw$NDcR939aR9hUMEJB4Z6rZ.:14279:0:99999:7:::
(We can use single user mode to change the password.)


C)In this file 2 field should have (x)
#head -1 /etc/passwd
root:!!:0:0:root:/root:/bin/bash

ANS :-change as follows.
#vim /etc/passwd
root:x:0:0:root:/root:/bin/bash



D)Check login shell.
It should contain a valid shell path.
root:x:0:0:root:/root:/sbin/false
root:x:0:0:root:/root:/sbin/nologin
root:x:0:0:root:/root:/dev/zero
root:x:0:0:root:/root:/dev/null

ANS is :- change the shell to a valid one
root:x:0:0:root:/root:/bin/bash



E)TO check valid shells prefer.
#vim /etc/shells

check /etc/securetty
#vim /etc/securetty
no lines should be commented.

To check the permissions of /etc/securetty
#ls -l /etc/securetty
-rw------- 1 root root 122 Feb  4 21:54 /etc/securetty
permission should be 600.If something else then correct it.

4)EXAMPLE :-

Foult.

#chmod 777 /etc/securetty
#ls -l /etc/securetty
-rwxrwxrwx 1 root root 122 Feb  4 21:54 /etc/securetty

Solution.

#chmod 600 /etc/securetty
-rw------- 1 root root 122 Feb  4 21:54 /etc/securetty


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QUE 3) :- DIG PROBLEM

Dig problem.

1)Add DNS server ip in /etc/resolv.conf
ANS :-
#vim /etc/resolv.conf
nameserver (server ip)

how to fet the DNS server ip?
1)network.txt file --given by examiner in system.
2)

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QUE 4) :- DISK QUOTA

*Disk Quotas problems.


1)To create the users.
#useradd neo

2)To assigne quota
#vim /etc/fstab
LABEL=/home             /home               ext3    defaults,usrquota,grpquota        1 2

#mount -o remount,usrquota,grpquota /home/

3)to check
#mount

4)To create quota files.
#quotacheck -cugv /home

5)To switchon the quota.
#quotaon /home/

6)To check the quota.
#repquota -a

7)To assigne the quota.
#edquota -u (user)neo
Disk quotas for user neo (uid 706):
  Filesystem                   blocks       soft       hard     inodes     soft     hard
  /dev/sda7                     16           0          70          6        0        0

8)To login by user.
#su - neo
$dd if=/dev/zero of=/home/neo/somefile bs=70k count=1

$ll -h
$quota -v
$rm -f somefile

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QUE 5) :- LVM

Resize lv upto 500mb.

200mb to 500mb.
first to check the space is availabel in Volume Group for resize the lv.
If no space so first create the partition & convert that partition into pv & add into vg.
If space is availabel so go for the lvresize.

1)To create partition.
#fdisk /dev/sda

*To create partition.

2)To update the partition table.
#partprobe /dev/sda

3)To create physical volume.
#pvcreate /dev/sda12

 Physical volume "/dev/sda12" successfully created

4)To create volume group.
#vgextend vg0 /dev/sda12

 Volume group "vg0" successfully created

5)To resize the Logical Volume.
#lvresize -L +300mb /dev/vg0/lvm1
 Extending logical volume raj to 300.00 MB
 Logical volume raj successfully resized

6)To check.
#lvdisplay

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By Laxman D. Kadam.

Ph No:- 9967413230

Email:- vikasjk3@gmail.com