Linux

This is set of Linux question commonly being asked.

What is the reason for the boot space to fill up after patching?

This is because a new version of Kernel is being put into boot directory if it’s being updated.

What would you do if after Linux patching you have a Kernel Panic

Reload the system using previously Kernel. Read on the screen error information and make a copy it.

Recover system from snapshot if everything else failed.

What is a TTL in DNS/Bind configuration on Linux.

TTL – Time to live. This is a time when zone expires and dns refreshing their information.

What is a difference between recursive and authoritative DNS.

Recursive DNS can provide information about other domain servers. Authoritative DNS is the DNS server which keeps the domain zone.

Explain in details what is happening when a request is made to google.com in laptop/dns recursive configuration?

A quick answer is that a dns request is made from laptop to dns server. If the dns server does keep the cache of the domain then a request is made to authoritative dns or root dns. server. Once ip is resolved that information goes back to your laptop.

(Please keep in mind that that this is a very basic answer)

What is a DNSSEC?

DNSSEC is a security extension to Bind to provide extra layer of security. More info:

https://www.icann.org/resources/pages/dnssec-qaa-2014-01-29-en

In which file a DNS server is configured in Linux?

Normally it’s located under /etc/resolv.conf with the following content (the below is just for info and your file content will definitely differ from the one below)

search example.com local.lan
nameserver 127.0.0.1
nameserver 172.16.1.254
nameserver 172.16.2.254
nameserver 192.168.137.2

Troubleshooting:

Why does X fail after processing for Y hours?

How can we run X so the job completes faster?

Why is the X download failing?

Other information:

Software installation(Packages/Binaries/Source)

OS Patching

Resizing NFS shared disks
CloudWatch monitoring/alerts
Creating/Resizing Amazon Cloud Desktop instances (look at ThinLinc)

Usefull Linux Command:

sed -e ‘/^#/d’ -e ‘/^$/d’ /etc/zabbix/zabbix_agentd.conf – display configuration without comments.

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