[mdlug] Job Interview Questions: Linux Admin

[Gib]

These all sound like good answers. Some of these could be written into the
normal operations documents.

On Wed, Nov 30, 2022 at 7:11 AM Carl T. Miller <carl at carltm.com> wrote:

> On 11/29/22 06:56 PM, Gib wrote:
>
> Hey Gib,
>
> Good questions.  Here are some things to consider.
>
> c
>
> > What would you do to diagnose a slow system?
>
> 0.  First, talk to the person(s) who are experiencing
> the issue.  When and how do they notice the slowness?
> Is it constant or cyclical?  If constant, has it started
> recently or has it worsened over time?  If cyclical,
> try to determine when it starts, how long it lasts,
> and when it stops.  Is there anything they can do
> (such as a reboot) that can bring it back up to speed?
>
> 1.  Check if it's swapping.  If it is, find what is eating
> the memory and either decide to offload that program
> or to buy more memory.
>
> 2.  Run atop to see if there is currently a bottleneck.
> If so determine what is the best method to alleviate
> it.  Perhaps add a network card, buy faster hard
> drives, etc.
>
> 3.  Examine what programs are running and what
> resources they need.  It's possible there is an
> update to the current software or a better program.
> Likewise for the operating system and the kernel.
> It may benefit from changing the process scheduler,
> tweaking the kernel and/or drivers.
>
> 4.  Run sa and check the results after a day, a week,
> a month and a year.  It is possible that the slowness
> only occurs as certain tasks run.
> If restoring a prior backup of
> 5. Do more advanced monitoring if needed.
>
> > How would you do a performance problem when more swap space needs to be
> > added?
>
> Actually I'd go through the same steps as above,
> but focus on memory and software.
>
> > How would you handle a root password loss?
> I would check with each user and recent backups if
> available.  The goal would be to find the password
> or to determine when it was most recently changed.
>
> Next check the permission in pam and/or selinux to
> see if there are restrictions.  Perhaps it may be
> necessary to use ssh with a key or to use a particular
> tty.
>
> Check if there are any other accounts with id 0 that
> can be used.  Also, check for sudo access by any of
> the users.
>
> If all else fails, try going to runlevel 1 and hope
> that you have the right grub password, if needed.
> If that fails, boot from a system recovery image
> and hope that you have the right encryption
> passphrase, if needed.
>
> In any case, after updating the password, I'd
> enable sudo for the appropriate users and then
> lock down the root account.  I would then ask
> for two people (manager and a vp?) who would
> receive a sealed envelope to be kept in a safe
> that contains instructions to gain access as
> root.  All "normal" admins would then be
> required to use their personal account and
> the root account.
>
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