Seasoned Linux professionals thoroughly know data formats: it is mandatory since these formats are used by many tools as:
- output format (CSV, XML, JSON, …)
- the format for their settings files (YAML, TOML, XML, JSON, INI, …)
- the format of the document to be sent to an API (XML by SOAP, JSON by REST)
It is straightforward that is mandatory to be familiar to Regular Expressions: many legacy tools like grep (in all of its flavours, such as egrep) and sed use them as pattern matching criteria. They should also know how to leverage on awk when a little bit of business logic is needed while processing data, and of course know most of the so called “coreutils” (sort, cut, wc, uniq, …). Modern Linux professionals are also skilled on format specific tools such as xpath and xmlstarlet (XML), jq (JSON) or yq (YAML).
In addition to that, Linux professionals should also have a thorough understanding of:
- encryption technologies that guarantee data integrity and confidentiality on the disk (openssl, GPG, PGP, …)
- encryption technologies that guarantee data integrity and confidentiality on the wire (TLS, X.509 certificates, Public Key Infrastructure
- design patterns that exploit encryption technologies, such as Shamir’s Secret Sharing
- Cryptographic API, such as PKCS#11
Honestly, in my experience, I saw too many technicians neglecting this topic, but believe me, this can be very dangerous.