Interview: sysadmin

Command line tools

Which tools have you used in below categories? With which options? What do the options perform? (possible answers/options listed after category)

  * network tools

    * iftop: n, N, P
    * lsof: i, p, c, N, P
    * tcpdump: n, host, net, and, or
    * iptables: t, L, n, D
    * dig: txt, mx, a, cname
    * ping
    * traceroute/mtr

  * filesystem tools

    * df: h, a, s, T
    * du: s, h
    * fdisk: l
    * mkfs
    * find: exec, name, type
    * updatedb/locate

  * monitoring tools / process management

    * watch: d, n
    * ps: a, u, x, w
    * htop
    * vmstat: <seconds>
    * sa/sar
    * nice
    * smartctl
    * iostat: <seconds>, x, m


* Filesystems

  * Which are the types of filesystems: ext3, ext4, xfs, brtfs
  * What is an inode? How would you handle a "disk full" error related to inodes usage?


* Networking

  * What is port forwarding and how have you used it?
  * What is CIDR, show examples?
  * What is NAT? How have you used NAT technology?
  * What are the types of protocols? Explain their use. (tcp, udp, icmp)
  * Which hardware/software firewalls have you used? Explain.
  * Have you used VPN technology? Explain what was done and how you were involved.


* AWS

What is your experience with AWS? Detail/diagram projects.

Which AWS technologies have you used?

  * EC2

    * How have you managed AWS servers: API, web interface, command line tools?
    * Which types of instances have you used?
    * How many servers were you responsible for?
    * What is the difference between EBS and ephemeral storage? Pros/cons.

  * EBS

    * Which parameters does volume creation require?
    * What is a snapshot? How are redundant blocks stored for subsequent snapshots?

  * ELB

    * What is the "health check" used for? What are the parameters
    * Have you used SSL with ELB?
    * What are "listeners"?
    * Have you used ELB in conjunction with haproxy. Diagram.

  * VPC

    * How did you use VPC? Have you setup a AWS VPC from scratch?
    * Do you know what a "DHCP option set" is? How is it used?
    * Diagram what subnets were used, which were public, and which private.

  * SES

    * What is a "verified" email or domain in SES?

  * Route 53

    * Have you created a domain in Route 53?
    * Have you maintained DNS records with Route 53?
    * What does Route 53 offer that other DNS services do not?
    * How does Route 53 integrate with AWS ELB technology?

Monitoring

  * CloudWatch

    * How did you use CloudWatch to monitor server health and network use
    * Did you ever setup a CloudWatch email alert? Explain steps involved.

  * Zenoss

    * What are the tools you used in Zenoss
    * How large was the monitored infrastructure?
    * What is a Zenoss event?

  * On-call

    * Talk about your past on-call experiences, and one time handled a major issue
    * What are the available paging services, and which have you used?

Java

  * What experience do you have installing/supporting Java?
  * Explain how you performed JVM monitoring.
  * Tomcat
    * Have you ever supported Tomcat? What were the configurations you were responsible for?
    * What are the core Tomcat configuration files? Log files?
  * What is the Java Heap? How can this be set/modified, and what are the effects? Downsides?
  * What steps would you take to debug/resolve a "Out of Memory" JVM error?

Cassandra

  * Explain your experience with Cassandra. Versions?
  * How many nodes did you support? What percent of the data load was each node responsible for?
  * nodetool: what are the options, and what do they show/perform?
  * Explain how you built a ring from the ground up in the past
  * What steps did you take to monitor your Cassandra nodes?
  * What steps did you take for a node failure?
  * How did you find/get answers to questions you had on the Cassandra techonology?

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