Kategori
Operations & Fieldcraft
Alle værktøjer og artikler i denne kategori, samlet ét sted.
Værktøjer
Before/After Health Snapshot Comparator
You declare the states, the tool gates the conclusion: seven selections produce a tiered comparison report - baseline quality, a churn-classed dimension catalog, delta-interpretation guidance, and the continue / observe / investigate / hold-rollback-ready gate. Never labels a change successful on green components alone.
Change Blast-Radius Mapper
Describe what you are changing and its structure; a fixed rule set maps the blast radius as concentric tiers (target, co-located, downstream, human) populated with what could be affected, plus severity-tagged risks and containment measures. It maps what could be affected, never asserts what will break.
Change Window Runbook Builder
Describe a planned change in six structured fields; a fixed rule set assembles an ordered runbook across six phases - with the risks the plan carries and readiness cautions about the input. Advisory structure to review and adapt, never an approval.
chmod permission calculator
Type a file mode as octal (4755), as ls shows it (-rwsr-xr-x) or as chmod clauses on a base (g+s,o-rwx) and read it every other way: the bits, who may do what, what setuid, setgid and the sticky bit mean for a file or a directory, the commands that reach it, the umask that would create it, and a trace of each clause. From POSIX.1-2024 chmod and ls and coreutils 9.11 chmod(1); nothing leaves the browser.
Digital transformation tracker
Thirty milestones across seven domains, sorted by how much you should trust them: what shipped, what is already law, what is scheduled, what is scheduled but actively moving, and what is only somebody's forecast.
Fault Hypothesis Builder
Describe a fault in six structured fields; a fixed rule set ranks hypotheses to test - with the evidence to collect, what would support each, and what would weaken it. Advisory structure, never a diagnosis.
Flow Path Reasoner
The senior skill is refusing to troubleshoot until the path is understood. Seven selections build a canonical hop map with side-flows, TLS segments, rewrite points, and ranked failure-domain candidates - and unknowns stay visibly unknown.
Incident Timeline & RCA Builder
RCA stands for root cause analysis - the disciplined walk from an incident's symptoms back to the conditions that allowed it. Enter an incident's events as a small timeline and mark the contributing-factor domains you observed; a fixed rule set orders the timeline, derives the milestone spans, and structures candidate contributing factors with the evidence for each. It never names a root cause - candidates to investigate, not a verdict.
Log level mapper
Pick a level in one logging system (syslog, the Linux kernel, Cisco IOS, Junos, Windows Event Log, .NET, Python, java.util.logging, Log4j 2, OpenTelemetry) and read its nearest equivalent in every other, with each system's own number and words, where the match is exact and where it is only the nearest rung. The bridge is OpenTelemetry's SeverityNumber, the one scale defined to hold the others. Nothing is sent anywhere.
Network operating system comparer
Fourteen network operating systems - IOS, IOS XE, IOS XR, NX-OS, Junos, Junos Evolved, EOS, TMOS, F5OS, EXOS, VOSS, FortiOS, PAN-OS and Gaia - with lineage, what each runs on, how components share state, where the planes divide, and what an upgrade costs. Pick one for a full profile or two to see them axis by axis. Every entry lists weaknesses as well as strengths.
Packet Capture Plan Builder
Command builders answer how to capture; this answers where, why, and what it would mean. Describe the path and the symptom; a 35-rule original registry designs a phased capture plan: ranked points on named boundaries, expected observations, an interpretation matrix with supports and weakens decided before collection, and sync/authorization discipline. It plans captures - it never ingests them.
Python playground
Real CPython 3.14 in your browser, for the arithmetic of networks: subnets, masks, EUI-64, DNS headers in struct, HMAC, latency statistics, transfer times. A 13.5 MB engine downloads once, when you say so; nothing you type leaves the page.
Syslog message parser
Paste one syslog message, or a TCP frame carrying one, and read every field named in the order its RFC names them: the PRI opened into facility and severity, the RFC 5424 header, the structured data element by element, the message; or the BSD form of RFC 3164 with its TIMESTAMP, HOSTNAME, TAG and CONTENT. Whatever is non-compliant is said in the RFC's own words. Nothing is sent anywhere.
TAC Escalation Packet Builder
Describe the issue you are about to escalate; a fixed rule set assembles a complete vendor-support packet and a checklist of the artifacts still to collect before opening the case, dropping what you already have. It structures the hand-off; it does not open a case or contact any vendor.
Terminal, shell, TTY and console explainer
Paste what `tty` printed - /dev/pts/3, /dev/tty2, /dev/ttyS0, /dev/tty, /dev/console, or “not a tty” - and see which layer you are actually looking at, what is holding the other end, and what that implies for signals, job control and what happens when the window closes. Local and offline.
Artikler
From First Symptom to a TAC Case That Does Not Bounce
Five steps that never name a root cause. The discipline is keeping what you observed separate from what you concluded, because an escalation that mixes them is an escalation that comes back asking for the difference.
LæsPlanning a Change, and the Step Everyone Skips
Map the reach, write the runbook with its rollback, then compare health before and after. The third step is the one that gets dropped, and it is the only one that can tell you the change did what you said it would.
LæsGit: the content-addressed database wearing a version-control suit
What Git actually stores (snapshots, not diffs), why a branch is just a 41-byte pointer, how the three areas explain almost every confusing command, and what made a two-week side project the industry's default in fifteen years.
LæsGitHub: the pull request was the product
Git solved copying; GitHub solved coordinating. How a 2008 Rails app turned the emailed patch into a reviewable conversation, made a profile into a résumé, accreted a platform around the repository, and became the largest code host in the world without ever owning the protocol underneath it.
LæsTerminal, shell, TTY, console
Four words used interchangeably by almost everyone, including the documentation. They name four different things, and the distinction explains why Ctrl+C kills your command but not your shell.
LæsWhat a Channel Systems Engineer Actually Does
Inside a distributor there is a role almost nobody outside the channel can describe: the systems engineer who supports resellers rather than customers. Bill of materials work on every project that passes through, proofs of concept, presentations, enablement, bootcamps, trade shows. Some of the resellers being supported have no technical staff at all, which is the fact that explains the rest of the job.
LæsWhat a network operating system actually is
IOS, Junos, EOS, TMOS, FortiOS, PAN-OS and the rest, compared on the axes that matter: what they run on, how components share state, where the planes divide, and what happens when one part fails.
LæsThe path a product takes, and the jobs along it
Between the company that builds a thing and the person who depends on it, a product passes through many hands. Each pair belongs to a job with its own clients, suppliers, accountability and measurement, and the measurement is rarely the same as the accountability.
Læscron: five fields that run the world's chores
Every Unix box carries a scheduler whose entire language is five columns of numbers and stars. How to read them, the OR rule that catches almost everyone, why 0 and 7 are the same day, what the @ macros expand to, and the local-time reality behind every projected run.
LæsOpen source, and the two meanings of free
English overloads one small word, and forty years of software history hang on the ambiguity. The four freedoms, the 1998 rebrand that created 'open source', copyleft versus permissive, why gratis is not libre, and why Portuguese speakers never had this problem in the first place.
LæsDecided in advance: the five practices the failures argue for
Two companion pages collect what broke and what got said. This one is the third question: what has to be decided before anything happens, because it cannot be decided during. Five practices, each paired with the case that demonstrates the cost of not having it - a baseline, a blast radius, a change window, a restorable backup, and a boundary.
LæsHow to independently review a network architecture before approving it
A design arrives with a diagram, a bill of materials and a date. Approving it is a decision with years of consequences, and the material in front of you was prepared by people who want it approved. A method for reading it on your own terms: what to ask for before you start, the seven questions that find most problems, how to separate what the design says from what it assumes, and what a written review should contain so the approval survives the person who gave it.
LæsHow to find the hidden assumptions in an architecture diagram
A diagram shows what was decided and hides what was assumed. The boxes are products, the lines are intentions, and the things that will actually fail, the shared dependency, the unmeasured peak, the function nobody owns, the path that only works one way, are not drawn because nobody thought of them as decisions. Eight places assumptions hide in a diagram, the questions that bring each one out, and the register that turns a reading into something the organisation can act on in year three.
LæsWhat should be in a post-incident technical review
After a serious outage somebody has to write down what happened, and the document that results is usually either a defence or a prosecution. A technical review is neither. It is written for people who were not there, it keeps what was observed apart from what was concluded, it names the conditions that made the failure possible rather than the person who touched the keyboard, and it ends in changes that can be checked. What such a review contains, who should write it, and the three kinds of review that must not be confused.
LæsHow to separate product limitations from architecture failures
When something fails, the first explanation on the table is the product, because the product has a vendor and the vendor has a support line. Often the product did exactly what it was built to do, inside a design that asked it to do something else. Telling the two apart matters, because the fix for a product limitation is a case, a patch or a replacement, and the fix for an architecture failure is a change to the design, and buying a new product to fix a design is the most expensive way to keep the problem. A method for making the distinction, with evidence.
LæsWhat executives should ask before approving a network transformation
A transformation programme arrives at the executive table as a vision, a supplier, a budget and a date, and the technical detail underneath it is exactly what the people at the table were hired not to need. They do not need it. They need twelve questions whose answers tell them whether the detail was done, who is carrying which risk, what the organisation will be unable to undo, and what the first ninety days will cost in attention. The questions, why each one matters, and what a good answer sounds like.
LæsFile modes, read the way the kernel reads them: octal, symbolic, and the three bits most people skip
A Unix file mode is twelve bits, and almost every permission mistake comes from reading nine of them. Where 755 comes from, why ls prints an s or a T, what set-user-ID, set-group-ID and the restricted deletion flag do on a file and on a directory, how a chmod clause with no class is quietly filtered through the umask, why X is not x, and the GNU rule that keeps a directory's set-group-ID bit when you type chmod 755. From POSIX.1-2024 and coreutils 9.11, with the calculator to try each case.
LæsReading a syslog message field by field: what a parser checks, and where each rule comes from
An RFC 5424 message is seven header fields, a structured-data block and a free-text tail, and every one of them has a rule a parser can test: the leading-zero rule of the PRI, the upper-case T and Z of the timestamp, the 48-character APP-NAME, the escapes inside structured data, the byte order mark that announces UTF-8, the 480 and 2048 octet lines, and the two ways a message is framed on TCP. Read from the RFCs themselves, with the parser that applies each rule as you go.
LæsLog levels across systems: one scale, many ladders
Syslog counts down from 0, Python counts up in tens, Log4j gives FATAL the smallest number and TRACE the largest, Windows puts Critical at 1 and java.util.logging puts SEVERE at 1000. Every system has a ladder, no two ladders agree on direction or spacing, and the same word lands in different places. OpenTelemetry's SeverityNumber is the one scale written to hold them all, and this article walks the ten ladders the mapper knows, where each rung lands, and where the mapping is a judgement rather than a fact.
LæsAccounting: who did what, to which device, and when
The third A of AAA as an engineering design rather than a checkbox: the four record streams that together answer the question asked after every outage and every intrusion, RADIUS accounting from RFC 2866, TACACS+ command accounting from RFC 8907, syslog from RFC 5424 and the device's own configuration change log, plus configuration backups that show what the commands did; what each record contains, field by field; the NIST SP 800-53 controls that say what a record must establish; the clocks, retention, correlation keys and separation of duties that make the records usable; and the oldest finding in the field, the device that was never told where to send them.
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