Interview Q&A / Linux & Shell

1. How do you check disk space and memory usage on a Linux server?

   Use df -h to see free space on each mounted file system, du -sh to see how much space a folder takes, and free -h to see RAM and swap. In free, look at the "available" column, not "free", because Linux uses spare RAM as disk cache and gives it back when programs need it.

   IntermediateIn-depth3 min read
2. How do you check whether a remote port is reachable from a Linux machine?

   Use nc -zv host port for a quick TCP check, or curl -v telnet://host:port, or bash's /dev/tcp. A refused connection means nothing listens there; a timeout usually means a firewall or routing problem. ping only tests ICMP, not ports.

   IntermediateQuick answer1 min read