Update content for gemtext

10 files changed, 740 insertions, 372 deletions

diff --git a/gemfeed/2026-05-08-unveiling-ior-ng-part-1.gmi b/gemfeed/2026-05-08-unveiling-ior-ng-part-1.gmi
index 09e0e133..84b25457 100644
--- a/gemfeed/2026-05-08-unveiling-ior-ng-part-1.gmi
+++ b/gemfeed/2026-05-08-unveiling-ior-ng-part-1.gmi
@@ -1,4 +1,4 @@
-# Unveiling I/O Riot NG 1.0.0 — Part 1: a guided tour
+# Unveiling I/O Riot NG — Part 1: a guided tour
 
 > Published at 2026-05-07T09:46:29+03:00
 
@@ -8,14 +8,15 @@ This is the first of three posts. Part 1 is the demo-driven tour: what `ior` loo
 
 => ./unveiling-ior-ng/00-hero-flamegraph.png Live flamegraph
 
-=> ./2026-05-08-unveiling-ior-ng-part-1.gmi 2026-05-08 Unveiling I/O Riot NG 1.0.0 — Part 1: a guided tour (You are currently reading this)
+=> ./2026-05-08-unveiling-ior-ng-part-1.gmi 2026-05-08 Unveiling I/O Riot NG — Part 1: a guided tour (You are currently reading this)
+=> ./2026-05-11-unveiling-ior-ng-part-2.gmi 2026-05-11 1) Enable repos and install build dependencies. CRB ships zlib-static / glibc-static.
 
 => https://codeberg.org/snonux/ior I/O Riot NG on Codeberg
 => ./2018-06-01-realistic-load-testing-with-ioriot-for-linux.gmi the original I/O Riot post (2018)
 
 ## Table of Contents
 
-* ⇢ Unveiling I/O Riot NG 1.0.0 — Part 1: a guided tour
+* ⇢ Unveiling I/O Riot NG — Part 1: a guided tour
 * ⇢ ⇢ What it does
 * ⇢ ⇢ First launch
 * ⇢ ⇢ The seven tabs, in 30 seconds each
@@ -201,16 +202,22 @@ Once a parquet file is on disk, point any SQL-over-parquet tool at it — Part 3
 
 But the live flamegraph, the stackable stream filters, and the cheap parquet capture together cover the cases I actually hit week to week. The demo above is the easiest way to get a feel for whether it's the kind of tool you want.
 
-For installing it and the eBPF / CO-RE / static-linking story (why one build runs on every other Linux box you scp it to), see Part 2 (once published). For the per-event schema, async-syscall caveats, the probe-generator safeguard against missing new kernel syscalls, and post-mortem SQL on the parquet output, see Part 3 (once published.).
+For installing it and the eBPF / CO-RE / static-linking story (why one build runs on every other Linux box you scp it to), see Part 2. For the per-event schema, async-syscall caveats, the probe-generator safeguard against missing new kernel syscalls, and post-mortem SQL on the parquet output, see Part 3.
 
 => https://codeberg.org/snonux/ior Source on Codeberg
 => https://codeberg.org/snonux/ior/src/branch/main/docs/tutorial/tutorial.md The full in-repo tutorial
 
+Read the next post of the series:
+
+=> ./2026-05-11-unveiling-ior-ng-part-2.gmi  Unveiling I/O Riot NG — Part 2: install and compile once, run everywhere
+
+
 E-Mail your comments to `paul@nospam.buetow.org` :-)
 
 Other related posts are:
 
-=> ./2026-05-08-unveiling-ior-ng-part-1.gmi 2026-05-08 Unveiling I/O Riot NG 1.0.0 — Part 1: a guided tour (You are currently reading this)
+=> ./2026-05-11-unveiling-ior-ng-part-2.gmi 2026-05-11 1) Enable repos and install build dependencies. CRB ships zlib-static / glibc-static.
+=> ./2026-05-08-unveiling-ior-ng-part-1.gmi 2026-05-08 Unveiling I/O Riot NG — Part 1: a guided tour (You are currently reading this)
 => ./2018-06-01-realistic-load-testing-with-ioriot-for-linux.gmi 2018-06-01 Realistic load testing with I/O Riot for Linux
 
 => ../ Back to the main site
diff --git a/gemfeed/2026-05-08-unveiling-ior-ng-part-1.gmi.tpl b/gemfeed/2026-05-08-unveiling-ior-ng-part-1.gmi.tpl
index 71aa9659..02b0c2b8 100644
--- a/gemfeed/2026-05-08-unveiling-ior-ng-part-1.gmi.tpl
+++ b/gemfeed/2026-05-08-unveiling-ior-ng-part-1.gmi.tpl
@@ -1,4 +1,4 @@
-# Unveiling I/O Riot NG 1.0.0 — Part 1: a guided tour
+# Unveiling I/O Riot NG — Part 1: a guided tour
 
 > Published at 2026-05-07T09:46:29+03:00
 
@@ -186,11 +186,16 @@ Once a parquet file is on disk, point any SQL-over-parquet tool at it — Part 3
 
 But the live flamegraph, the stackable stream filters, and the cheap parquet capture together cover the cases I actually hit week to week. The demo above is the easiest way to get a feel for whether it's the kind of tool you want.
 
-For installing it and the eBPF / CO-RE / static-linking story (why one build runs on every other Linux box you scp it to), see Part 2 (once published). For the per-event schema, async-syscall caveats, the probe-generator safeguard against missing new kernel syscalls, and post-mortem SQL on the parquet output, see Part 3 (once published.).
+For installing it and the eBPF / CO-RE / static-linking story (why one build runs on every other Linux box you scp it to), see Part 2. For the per-event schema, async-syscall caveats, the probe-generator safeguard against missing new kernel syscalls, and post-mortem SQL on the parquet output, see Part 3.
 
 => https://codeberg.org/snonux/ior Source on Codeberg
 => https://codeberg.org/snonux/ior/src/branch/main/docs/tutorial/tutorial.md The full in-repo tutorial
 
+Read the next post of the series:
+
+=> ./2026-05-11-unveiling-ior-ng-part-2.gmi  Unveiling I/O Riot NG — Part 2: install and compile once, run everywhere
+
+
 E-Mail your comments to `paul@nospam.buetow.org` :-)
 
 Other related posts are:
diff --git a/gemfeed/2026-05-11-unveiling-ior-ng-part-2.gmi b/gemfeed/2026-05-11-unveiling-ior-ng-part-2.gmi
new file mode 100644
index 00000000..d41084df
--- /dev/null
+++ b/gemfeed/2026-05-11-unveiling-ior-ng-part-2.gmi
@@ -0,0 +1,256 @@
+ (or Podman)# Unveiling I/O Riot NG — Part 2: install and compile once, run everywhere
+
+This is Part 2 of three. Part 1 is the demo-driven tour: what ior looks like, how the dashboard tabs work, how filtering and recording behave. This part is about the installation for Rocky Linux 8 and 9 and, more interestingly, why you only have to do that dance on a single machine: the resulting binary is portable to every other Linux box thanks to CO-RE (Compile Once, Run Everywhere) plus full static linking. Part 3 is the under-the-hood companion (per-event schema, async-syscall caveats, the syscall-coverage probe generator, and post-mortem SQL on the parquet output).
+
+=> ./2026-05-08-unveiling-ior-ng-part-1.gmi 2026-05-08 Unveiling I/O Riot NG — Part 1: a guided tour
+=> ./2026-05-11-unveiling-ior-ng-part-2.gmi 2026-05-11 1) Enable repos and install build dependencies. CRB ships zlib-static / glibc-static. (You are currently reading this)
+
+=> ./unveiling-ior-ng/00-logo.png I/O Riot NG logo
+
+## Table of Contents
+
+> Published at 2026-05-10T22:41:23+03:00
+
+> Published at 2026-05-10T22:39:24+03:00
+
+* ⇢ ⇢ Installing ior
+* ⇢ ⇢ ⇢ Why native installation is a mess
+* ⇢ ⇢ ⇢ What the Docker build is actually doing
+* ⇢ ⇢ A short detour: eBPF and libbpfgo
+* ⇢ ⇢ CO-RE — the part that makes the binary actually portable
+* ⇢ ⇢ ⇢ Static linking
+* ⇢ ⇢ ⇢ Go programs are statically linked by default
+* ⇢ ⇢ ⇢ `cgo` programs are not statically linked by default.
+* ⇢ ⇢ ⇢ CO-RE
+* ⇢ ⇢ A note on cgo overhead
+* ⇢ ⇢ If you want to go deeper
+
+## Installing ior
+
+The short answer: Use Docker (or Podman). One command, no toolchain setup, works from any Docker-capable Linux host with BTF available:
+
+```sh
+git clone https://codeberg.org/snonux/ior ~/git/ior
+cd ~/git/ior
+mage buildDocker
+```
+
+First run builds a Rocky Linux 9 builder image (~15–20 minutes). Subsequent runs reuse the cached image and finish in under a minute. The resulting static binary is `./ior`. That's the officially supported install path, and it's the right one for anyone who just wants to run `ior` without living in its build system.
+
+> Note: There's also a target for building it for Rocky Linux 8.
+
+### Why native installation is a mess
+
+If you're curious why Docker became the answer, the native install on Rocky Linux 9 illustrates the problem well. Three separate things bite you before you even get to `mage build`:
+
+Rocky 9 ships neither `libelf.a` nor `libzstd.a`. There are no `*-static` subpackages for either, only the dynamic `.so` files. Both have to be compiled from source. `libelf` from the elfutils source RPM, `libzstd` from the upstream GitHub release tarball.
+
+Rocky 9 also only ships Go 1.25.x, but `ior` requires 1.26+ (due to improved CGo performance). So Go itself has to be installed from go.dev in parallel with the library builds.
+
+### What the Docker build is actually doing
+
+The Dockerfile encodes exactly the same steps that a native install on Rocky 9 would require. Here is the full sequence so you have a mental model of what's inside the image, and so you could reproduce it on a bare host if you ever needed to:
+
+```sh
+# 1) Enable repos and install build dependencies. CRB ships zlib-static / glibc-static.
+sudo dnf config-manager --set-enabled crb
+sudo dnf install -y epel-release
+sudo dnf install -y gcc clang bpftool elfutils-libelf-devel zlib-static \
+    glibc-static libzstd-devel git make cmake wget rpmdevtools strace bpftrace
+sudo dnf builddep -y elfutils
+
+# 2) Install Go 1.26 from go.dev. Rocky 9 ships only Go 1.25.x, ior needs 1.26+.
+cd /tmp
+wget -q https://go.dev/dl/go1.26.2.linux-amd64.tar.gz
+sudo tar -C /usr/local -xf go1.26.2.linux-amd64.tar.gz
+echo 'export PATH=/usr/local/go/bin:$HOME/go/bin:$PATH' | sudo tee /etc/profile.d/go.sh
+source /etc/profile.d/go.sh
+
+# 3) Build libelf.a from the elfutils source RPM.
+mkdir -p ~/src && cd ~
+dnf download --source elfutils-libelf
+rpm -ivh elfutils-*.src.rpm
+tar -C ~/src -xjf rpmbuild/SOURCES/elfutils-*.tar.bz2
+cd ~/src/elfutils-*
+./configure --enable-deterministic-archives --disable-debuginfod --disable-libdebuginfod
+make -C lib -j$(nproc)
+make -C libelf -j$(nproc)
+sudo cp -v libelf/libelf.a /usr/lib64/
+
+# 4) Build libzstd.a from upstream (libzstd-devel doesn't ship the static archive).
+cd /tmp
+wget -q https://github.com/facebook/zstd/releases/download/v1.5.5/zstd-1.5.5.tar.gz
+tar xzf zstd-1.5.5.tar.gz
+make -C zstd-1.5.5/lib -j$(nproc) libzstd.a
+sudo cp -v zstd-1.5.5/lib/libzstd.a /usr/lib64/
+
+# 5) Clone ior + libbpfgo, pin libbpfgo, build the static libbpf archive, install mage.
+mkdir -p ~/git
+git clone https://codeberg.org/snonux/ior ~/git/ior
+git clone https://github.com/aquasecurity/libbpfgo ~/git/libbpfgo
+git -C ~/git/libbpfgo checkout v0.9.2-libbpf-1.5.1
+git -C ~/git/libbpfgo submodule update --init --recursive
+make -C ~/git/libbpfgo libbpfgo-static
+go install github.com/magefile/mage@latest
+
+# 6) Generate the syscall-coverage handlers against THIS kernel and build.
+# IOR_FORCE_GENERATE bypasses the strict diff against the committed audit file
+# (the committed audit was generated against a different kernel build, and the
+# generator's safeguard would otherwise refuse to overwrite it).
+cd ~/git/ior
+env IOR_FORCE_GENERATE=1 GOTOOLCHAIN=auto mage generate
+# GOTOOLCHAIN=auto only required for an older version than 1.26 of GO.
+env GOTOOLCHAIN=auto mage all
+
+# 7) Smoke test.
+sudo ./ior -plain -duration 5
+```
+
+If you see `Probing for 5s` followed by CSV rows, the build is good. `mage buildDocker` runs all of this inside a container and hands you back just the final binary — the 15-minute first-run cost buys you never having to think about any of the above again.
+
+## A short detour: eBPF and libbpfgo
+
+If you haven't touched eBPF before: it's a small in-kernel bytecode VM. You compile a tiny C program, the kernel verifies it can't crash or loop forever, and then it runs every time some hook fires — a syscall enter/exit, a kprobe, a tracepoint, a network packet. The program writes events into a ring buffer that userspace mmaps and drains. No kernel module, no patched kernel, no debug symbols required.
+
+`ior` plugs into the syscall tracepoints (`sys_enter_openat`, `sys_exit_read`, etc.) and the BPF side does the bare minimum: timestamp the event, copy a few fields, push to a perf ring buffer. All the heavy lifting (string interning, latency math, aggregation, the dashboard) is in Go on the userspace side.
+
+The shape of the data flow:
+
+```
+ kernel space                  │  user space (Go)
+ ─────────────────             │  ──────────────────
+ syscall tracepoint            │
+ (sys_enter_openat,            │
+  sys_exit_read, …)            │
+        │                      │
+        │ fires                │
+        ▼                      │
+ BPF program (verified)        │
+   timestamp, copy fields      │
+        │                      │
+        ▼                      │
+ perf ring buffer ── mmap ─────┼──▶ ior reader goroutine
+                               │            │
+                               │            ▼
+                               │     intern strings,
+                               │     latency math,
+                               │     aggregate, render dashboard
+```
+
+The kernel ships a C library called libbpf that handles loading the program, attaching it to hooks, managing maps, and reading the ring buffer. There are two well-known ways to drive that from Go:
+
+* libbpfgo (Aqua Security): a thin cgo wrapper around libbpf. You ship libbpf along with your binary and call into the same C API that `bpftool` and `perf` use.
+* cilium/ebpf: a from-scratch pure-Go reimplementation of everything libbpf does (ELF parser, BTF resolver, syscall layer, the lot).
+
+I went with libbpfgo specifically because it's a wrapper, not a reimplementation.
+
+## CO-RE — the part that makes the binary actually portable
+
+The headline fact about `ior`'s deployment story: build it once on one box, then `scp ior other-host:/usr/local/bin/` to anywhere else and it just runs. No recompile per kernel, no kernel-debuginfo dance, no DKMS hooks. Two mechanisms make that work, and they reinforce each other.
+
+### Static linking
+
+The first is plain old static linking on the userspace side. A quick refresher on what that means, since it's central to why "scp the binary anywhere" works: when you build a normal Linux executable, the linker has two ways to wire library code into your program. Dynamic linking ("shared library") leaves a placeholder in the binary that says "at run time, find `libfoo.so.6` somewhere on `LD_LIBRARY_PATH` and pull in its symbols." Static linking pastes the library's machine code directly into your binary at build time, so there's nothing to look up later. Dynamic is smaller on disk and lets distros patch shared libs without rebuilding everything; static is bigger but self-contained, with no surprise about which version of the library the target box happens to have, no `error while loading shared libraries: libwhatever.so.6: cannot open shared object file` when the target ships a newer ABI.
+
+### Go programs are statically linked by default
+
+For Go, this is mostly a non-issue. A pure-Go binary (no cgo) is statically linked by default. The Go toolchain produces a single self-contained ELF file with no `.dynamic` section and no `NEEDED` entries. You can `scp` it to any Linux box of the same architecture and it just runs. That's one of the quietly nice things about Go.
+
+### `cgo` programs are not statically linked by default.
+
+`ior` is the not-quite-pure case: it goes through cgo to call into libbpf, libelf, and libzstd, and each of those has its own .so on the build host. By default cgo links those C dependencies dynamically, which would defeat the "scp the binary anywhere" property: the target box would need to have matching `.so` files at matching versions, which is exactly the kind of dependency hell Go usually saves you from. The fix is the line `-extldflags "-static"` in `ior`'s Magefile: it tells the external (C) linker to resolve `-lbpf -lelf -lzstd -lz` against the static archives (`.a` files) instead of the dynamic ones. That's why the install procedure above is so picky about having `libelf.a` and `libzstd.a` actually present on the build host. Without them the C-side static link fails.
+
+The result is a single ~23 MB binary with libbpf, libelf, libzstd, and zlib all baked in. None of them are looked up dynamically at runtime. The build host's library versions stay on the build host. (A couple of glibc resolver functions — `getpwnam_r` and friends — do still fall back to the target's libc, which is fine on any reasonable distro and is what the linker warnings during the build are about.)
+
+Pictorially, the three linking modes side by side:
+
+```
+ pure Go             cgo (default)                cgo + -extldflags "-static"
+ ┌────────┐          ┌────────┐                   ┌────────────────────────┐
+ │  ior   │          │  ior   │ ── libbpf.so.1 ?  │  ior + libbpf + libelf │
+ └────────┘          │        │ ── libelf.so.1 ?  │      + libzstd + libz  │
+   ~few MB           │        │ ── libzstd.so.1 ? └────────────────────────┘
+   one ELF,          └────────┘                     ~23 MB
+   no NEEDED         must find matching .so         one ELF,
+   entries           on the target box at runtime   no NEEDED entries
+```
+
+`ior` lives in the right-hand column.
+
+### CO-RE
+
+The second, and the one that's actually unusual, is CO-RE (Compile Once, Run Everywhere). CO-RE is the eBPF feature that solves the "the kernel changed its struct layout between releases" problem.
+
+The old I/O Riot was Systemtap. Systemtap programs are translated into a kernel module against the running kernel's exact headers, and that module then has to be loaded with `insmod`. That meant the user has to install a kernel-debuginfo package matching their running kernel, and a fresh build per host (or per kernel update).
+
+CO-RE throws all of that out. The idea, in one paragraph: when you write a BPF program that reads `task->mm->start_stack`, you don't bake the offsets of those fields into the compiled program. Instead, the compiler emits relocation records ("at this instruction, fetch the offset of `mm` inside `task_struct`"). At load time, libbpf looks up the actual offsets in the target kernel's BTF (BPF Type Format, a description of every kernel struct embedded in `/sys/kernel/btf/vmlinux` on any modern kernel) and patches the program in place. The same `.bpf.o` that ran on a 5.10 Debian kernel runs on a 6.8 Fedora kernel without recompilation.
+
+Pictorially, the contrast looks like this:
+
+```
+Old I/O Riot (Systemtap)                 New ior (libbpf + CO-RE)
+─────────────────────────                ────────────────────────────
+  .stp source                              .bpf.c source
+       │                                        │
+       │ needs THIS kernel's headers            │ build ONCE against vmlinux.h
+       │ + debuginfo package installed          │ (generated from any kernel BTF)
+       ▼                                        ▼
+  per-host translate + compile              one portable .bpf.o
+       │                                        │
+       ▼                                        ▼
+  per-host kernel module                    same binary on every host
+       │                                        │
+  insmod / modprobe                         libbpf loader:
+       │                                        │  • read /sys/kernel/btf/vmlinux
+       ▼                                        │  • patch field offsets
+  attached, this kernel only                    │  • verify + load
+                                                ▼
+                                          attached, runs anywhere
+```
+
+So the operational shape is: pick one box, do the install dance from the Rocky section above (or `docs/build-rocky-linux-9.md` for a native Fedora/RHEL build) once, build, then distribute the 23 MB binary wherever you want to trace. The build host needs Go and clang and the static libraries. The trace hosts need a BTF-enabled kernel and `sudo`. That's it.
+
+The whole "one build, every host" picture:
+
+```
+       build host                                trace hosts
+ ─────────────────────                     ─────────────────────────
+                                             ┌─────────────────┐
+                                             │  Rocky 8 box    │ sudo ior
+                                             │  kernel 4.18    │ ✓
+                                             └─────────────────┘
+ ┌──────────────────┐                        ┌─────────────────┐
+ │ Go + clang +     │   mage all             │  Debian 12 box  │ sudo ior
+ │ libelf.a +       │ ──────────▶ ior ──▶    │  kernel 6.1     │ ✓
+ │ libzstd.a +      │   23 MB static, CO-RE  └─────────────────┘
+ │ libbpf static    │      scp anywhere      ┌─────────────────┐
+ └──────────────────┘                        │  Fedora 39 box  │ sudo ior
+                                             │  kernel 6.8     │ ✓
+                                             └─────────────────┘
+                                          each: BTF-enabled kernel + sudo
+```
+
+## A note on cgo overhead
+
+The cost of being a libbpf wrapper rather than a pure-Go reimplementation is cgo. Every call from Go into libbpf crosses the cgo boundary, which historically meant tens to ~hundred-ish nanoseconds of overhead per call: register save/restore, a stack switch onto g0, goroutine state bookkeeping. Cheap in absolute terms, but it adds up if you call into C inside a tight loop. `ior` keeps the actual hot path on the kernel side and only crosses into Go once per drained batch of events from the ring buffer, so the per-call cost is amortized over thousands of events. In practice it doesn't show up in profiles.
+
+Go 1.26, the current release at the time of writing (early May 2026), is the one that finally took a serious bite out of cgo's per-call cost. The runtime can elide a chunk of the bookkeeping for calls that don't need it. Real-world wins depend heavily on the workload, but the rough direction is that cgo now feels closer to "an unusually expensive function call" than to "a context switch", which is the right mental model for almost everyone touching a C library from Go. The shorter version: cgo overhead used to be a real footgun for ports that called into C in the inner loop. With Go 1.26 it's a footnote unless you're doing many millions of small calls per second, in which case batching across the boundary still fixes it.
+
+## If you want to go deeper
+
+If any of this sounds interesting and you want to learn how to write your own BPF programs, two books are the standard recommendations and both well worth the time:
+
+* "Learning eBPF" by Liz Rice (O'Reilly, 2023) is the friendlier on-ramp. It walks through writing your first programs end-to-end, covers CO-RE and BTF in plain English, and is the book I'd hand to someone who has never touched the kernel side before. Liz also gave the canonical "what is eBPF" conference talk floating around YouTube, which makes a good 40-minute companion.
+* "BPF Performance Tools: Linux System and Application Observability" by Brendan Gregg (Addison-Wesley, 2019) is the encyclopedia. It's where you go after you've understood the basics and now want a complete reference for tracing every subsystem in the kernel — file systems, networking, scheduler, languages, applications — with worked tools for each. The flame-graph-driven analysis style throughout is also exactly how `ior`'s own flamegraph tab thinks about a workload.
+
+Between the two, Rice teaches you the moving parts and Gregg teaches you what to do with them.
+
+E-Mail your comments to `paul@nospam.buetow.org` :-)
+
+Other related posts are:
+
+=> ./2026-05-11-unveiling-ior-ng-part-2.gmi 2026-05-11 1) Enable repos and install build dependencies. CRB ships zlib-static / glibc-static. (You are currently reading this)
+=> ./2026-05-08-unveiling-ior-ng-part-1.gmi 2026-05-08 Unveiling I/O Riot NG — Part 1: a guided tour
+=> ./2018-06-01-realistic-load-testing-with-ioriot-for-linux.gmi 2018-06-01 Realistic load testing with I/O Riot for Linux
+
+=> ../ Back to the main site
diff --git a/gemfeed/DRAFT-unveiling-ior-ng-part-2.gmi.tpl b/gemfeed/2026-05-11-unveiling-ior-ng-part-2.gmi.tpl
index 07c41b0a..7539c969 100644
--- a/gemfeed/DRAFT-unveiling-ior-ng-part-2.gmi.tpl
+++ b/gemfeed/2026-05-11-unveiling-ior-ng-part-2.gmi.tpl
@@ -1,25 +1,20 @@
-# Unveiling I/O Riot NG — Part 2: install and compile once, run everywhere
+ (or Podman)# Unveiling I/O Riot NG — Part 2: install and compile once, run everywhere
 
-> Draft — not in the gemfeed yet. Promote with the usual rename + index dance.
+This is Part 2 of three. Part 1 is the demo-driven tour: what ior looks like, how the dashboard tabs work, how filtering and recording behave. This part is about the installation for Rocky Linux 8 and 9 and, more interestingly, why you only have to do that dance on a single machine: the resulting binary is portable to every other Linux box thanks to CO-RE (Compile Once, Run Everywhere) plus full static linking. Part 3 is the under-the-hood companion (per-event schema, async-syscall caveats, the syscall-coverage probe generator, and post-mortem SQL on the parquet output).
 
-This is Part 2 of three. Part 1 is the demo-driven tour: what ior looks like, how the dashboard tabs work, how filtering and recording behave. This part is about the install dance for Rocky Linux 9 (with one annoying kernel-backport caveat) and, more interestingly, why you only have to do that dance on a single machine: the resulting binary is portable to every other Linux box thanks to CO-RE (Compile Once, Run Everywhere) plus full static linking. Part 3 is the under-the-hood companion (per-event schema, async-syscall caveats, the syscall-coverage probe generator, and post-mortem SQL on the parquet output).
-
-If you came here for the dashboard tour, that's Part 1. If you want to know how the data pipeline is shaped, that's Part 3. This one is for the moment between "I want to try this" and "OK, it's running on the box I care about."
-
-=> ./DRAFT-unveiling-ior-ng-part-1.gmi Part 1: a guided tour
-=> ./DRAFT-unveiling-ior-ng-part-3.gmi Part 3: under the hood (schema, probe generator, ClickHouse)
-=> https://codeberg.org/snonux/ior I/O Riot NG on Codeberg
-=> ./2018-06-01-realistic-load-testing-with-ioriot-for-linux.gmi the original I/O Riot post (2018)
+<< template::inline::index unveiling-ior-ng
 
 => ./unveiling-ior-ng/00-logo.png I/O Riot NG logo
 
-<< template::inline::index unveiling-ior-ng
-
 << template::inline::toc
 
 ## Installing ior
 
-The short answer: use Docker. One command, no toolchain setup, works from any Docker-capable Linux host with BTF available:
+> Published at 2026-05-10T22:41:23+03:00
+
+> Published at 2026-05-10T22:39:24+03:00
+
+The short answer: Use Docker (or Podman). One command, no toolchain setup, works from any Docker-capable Linux host with BTF available:
 
 ```sh
 git clone https://codeberg.org/snonux/ior ~/git/ior
@@ -27,9 +22,9 @@ cd ~/git/ior
 mage buildDocker
 ```
 
-First run builds a Rocky Linux 9 builder image (~15–20 minutes). Subsequent runs reuse the cached image and finish in under a minute. The resulting static binary lands at `./ior`.
+First run builds a Rocky Linux 9 builder image (~15–20 minutes). Subsequent runs reuse the cached image and finish in under a minute. The resulting static binary is `./ior`. That's the officially supported install path, and it's the right one for anyone who just wants to run `ior` without living in its build system.
 
-That's the officially supported install path, and it's the right one for anyone who just wants to run ior without living in its build system.
+> Note: There's also a target for building it for Rocky Linux 8.
 
 ### Why native installation is a mess
 
@@ -37,9 +32,7 @@ If you're curious why Docker became the answer, the native install on Rocky Linu
 
 Rocky 9 ships neither `libelf.a` nor `libzstd.a`. There are no `*-static` subpackages for either, only the dynamic `.so` files. Both have to be compiled from source. `libelf` from the elfutils source RPM, `libzstd` from the upstream GitHub release tarball.
 
-Rocky 9 also only ships Go 1.25.x, but ior requires 1.26+. So Go itself has to be installed from go.dev in parallel with the library builds.
-
-And there's a kernel quirk that used to make this section much longer. Pre-fix, ior would happily load on a stock 5.14 RHEL kernel and then die on the very first tracepoint attach with `BPF_LINK_CREATE`/`BPF_PERF_EVENT` returning `EACCES`, even as root, with SELinux permissive, with every BPF-related sysctl wide open. The cause is that RHEL 9 carries an `rt`-tree backport that adds `preempt_lazy_count` to `struct trace_entry`. That widens the BTF-emitted alias `trace_event_raw_sys_enter`/`_exit` by 8 bytes and shifts the `args`/`ret` offsets, but the actual context the kernel hands the BPF program is still `struct syscall_trace_enter`/`_exit`, where the offsets did not move. Programs written against `trace_event_raw_sys_*` (the conventional choice; bcc, libbpf-tools, and ior all used to do this) end up reading past `max_ctx_offset`, so the verifier rejects the attach. The fix (also what bcc shipped in [PR #4920](https://github.com/iovisor/bcc/pull/4920) and what inspektor-gadget did) is to type the BPF context as `syscall_trace_enter`/`_exit` directly. ior now generates its handlers that way, and stock 5.14 RHEL/Rocky/Alma works without an ElRepo kernel.
+Rocky 9 also only ships Go 1.25.x, but `ior` requires 1.26+ (due to improved CGo performance). So Go itself has to be installed from go.dev in parallel with the library builds.
 
 ### What the Docker build is actually doing
 
@@ -93,6 +86,7 @@ go install github.com/magefile/mage@latest
 # generator's safeguard would otherwise refuse to overwrite it).
 cd ~/git/ior
 env IOR_FORCE_GENERATE=1 GOTOOLCHAIN=auto mage generate
+# GOTOOLCHAIN=auto only required for an older version than 1.26 of GO.
 env GOTOOLCHAIN=auto mage all
 
 # 7) Smoke test.
@@ -105,30 +99,76 @@ If you see `Probing for 5s` followed by CSV rows, the build is good. `mage build
 
 If you haven't touched eBPF before: it's a small in-kernel bytecode VM. You compile a tiny C program, the kernel verifies it can't crash or loop forever, and then it runs every time some hook fires — a syscall enter/exit, a kprobe, a tracepoint, a network packet. The program writes events into a ring buffer that userspace mmaps and drains. No kernel module, no patched kernel, no debug symbols required.
 
-ior plugs into the syscall tracepoints (`sys_enter_openat`, `sys_exit_read`, etc.) and the BPF side does the bare minimum: timestamp the event, copy a few fields, push to a perf ring buffer. All the heavy lifting (string interning, latency math, aggregation, the dashboard) is in Go on the userspace side.
+`ior` plugs into the syscall tracepoints (`sys_enter_openat`, `sys_exit_read`, etc.) and the BPF side does the bare minimum: timestamp the event, copy a few fields, push to a perf ring buffer. All the heavy lifting (string interning, latency math, aggregation, the dashboard) is in Go on the userspace side.
+
+The shape of the data flow:
+
+```
+ kernel space                  │  user space (Go)
+ ─────────────────             │  ──────────────────
+ syscall tracepoint            │
+ (sys_enter_openat,            │
+  sys_exit_read, …)            │
+        │                      │
+        │ fires                │
+        ▼                      │
+ BPF program (verified)        │
+   timestamp, copy fields      │
+        │                      │
+        ▼                      │
+ perf ring buffer ── mmap ─────┼──▶ ior reader goroutine
+                               │            │
+                               │            ▼
+                               │     intern strings,
+                               │     latency math,
+                               │     aggregate, render dashboard
+```
 
 The kernel ships a C library called libbpf that handles loading the program, attaching it to hooks, managing maps, and reading the ring buffer. There are two well-known ways to drive that from Go:
 
 * libbpfgo (Aqua Security): a thin cgo wrapper around libbpf. You ship libbpf along with your binary and call into the same C API that `bpftool` and `perf` use.
 * cilium/ebpf: a from-scratch pure-Go reimplementation of everything libbpf does (ELF parser, BTF resolver, syscall layer, the lot).
 
-I went with libbpfgo specifically because it's a wrapper, not a reimplementation. Whatever lands in libbpf upstream (new map types, new attach kinds, CO-RE fixes) I get for free the next kernel cycle. The pure-Go variant has to chase libbpf's feature set in parallel, and any divergence is on me to debug. For a tracer that's mostly value-add on the userspace side, "be a thin client of the kernel's own library" wins.
+I went with libbpfgo specifically because it's a wrapper, not a reimplementation.
 
 ## CO-RE — the part that makes the binary actually portable
 
-The headline fact about ior's deployment story: build it once on one box, then `scp ior other-host:/usr/local/bin/` to anywhere else and it just runs. No recompile per kernel, no kernel-debuginfo dance, no DKMS hooks. Two mechanisms make that work, and they reinforce each other.
+The headline fact about `ior`'s deployment story: build it once on one box, then `scp ior other-host:/usr/local/bin/` to anywhere else and it just runs. No recompile per kernel, no kernel-debuginfo dance, no DKMS hooks. Two mechanisms make that work, and they reinforce each other.
+
+### Static linking
 
 The first is plain old static linking on the userspace side. A quick refresher on what that means, since it's central to why "scp the binary anywhere" works: when you build a normal Linux executable, the linker has two ways to wire library code into your program. Dynamic linking ("shared library") leaves a placeholder in the binary that says "at run time, find `libfoo.so.6` somewhere on `LD_LIBRARY_PATH` and pull in its symbols." Static linking pastes the library's machine code directly into your binary at build time, so there's nothing to look up later. Dynamic is smaller on disk and lets distros patch shared libs without rebuilding everything; static is bigger but self-contained, with no surprise about which version of the library the target box happens to have, no `error while loading shared libraries: libwhatever.so.6: cannot open shared object file` when the target ships a newer ABI.
 
+### Go programs are statically linked by default
+
 For Go, this is mostly a non-issue. A pure-Go binary (no cgo) is statically linked by default. The Go toolchain produces a single self-contained ELF file with no `.dynamic` section and no `NEEDED` entries. You can `scp` it to any Linux box of the same architecture and it just runs. That's one of the quietly nice things about Go.
 
-ior is the not-quite-pure case: it goes through cgo to call into libbpf, libelf, and libzstd, and each of those has its own .so on the build host. By default cgo links those C dependencies dynamically, which would defeat the "scp the binary anywhere" property: the target box would need to have matching `.so` files at matching versions, which is exactly the kind of dependency hell Go usually saves you from. The fix is the line `-extldflags "-static"` in ior's Magefile: it tells the external (C) linker to resolve `-lbpf -lelf -lzstd -lz` against the static archives (`.a` files) instead of the dynamic ones. That's why the install procedure above is so picky about having `libelf.a` and `libzstd.a` actually present on the build host. Without them the C-side static link fails outright.
+### `cgo` programs are not statically linked by default.
+
+`ior` is the not-quite-pure case: it goes through cgo to call into libbpf, libelf, and libzstd, and each of those has its own .so on the build host. By default cgo links those C dependencies dynamically, which would defeat the "scp the binary anywhere" property: the target box would need to have matching `.so` files at matching versions, which is exactly the kind of dependency hell Go usually saves you from. The fix is the line `-extldflags "-static"` in `ior`'s Magefile: it tells the external (C) linker to resolve `-lbpf -lelf -lzstd -lz` against the static archives (`.a` files) instead of the dynamic ones. That's why the install procedure above is so picky about having `libelf.a` and `libzstd.a` actually present on the build host. Without them the C-side static link fails.
 
 The result is a single ~23 MB binary with libbpf, libelf, libzstd, and zlib all baked in. None of them are looked up dynamically at runtime. The build host's library versions stay on the build host. (A couple of glibc resolver functions — `getpwnam_r` and friends — do still fall back to the target's libc, which is fine on any reasonable distro and is what the linker warnings during the build are about.)
 
+Pictorially, the three linking modes side by side:
+
+```
+ pure Go             cgo (default)                cgo + -extldflags "-static"
+ ┌────────┐          ┌────────┐                   ┌────────────────────────┐
+ │  ior   │          │  ior   │ ── libbpf.so.1 ?  │  ior + libbpf + libelf │
+ └────────┘          │        │ ── libelf.so.1 ?  │      + libzstd + libz  │
+   ~few MB           │        │ ── libzstd.so.1 ? └────────────────────────┘
+   one ELF,          └────────┘                     ~23 MB
+   no NEEDED         must find matching .so         one ELF,
+   entries           on the target box at runtime   no NEEDED entries
+```
+
+`ior` lives in the right-hand column.
+
+### CO-RE
+
 The second, and the one that's actually unusual, is CO-RE (Compile Once, Run Everywhere). CO-RE is the eBPF feature that solves the "the kernel changed its struct layout between releases" problem.
 
-The old I/O Riot was Systemtap. Systemtap programs are translated into a kernel module against the running kernel's exact headers, and that module then has to be loaded with `insmod`. That meant the user has to install a kernel-debuginfo package matching their running kernel, and a fresh build per host (or per kernel update). On the BSD-style "you only run what you compiled here" laptop crowd that was tolerable; on a fleet of distros + kernel versions it was a recurring tax. Half of the original I/O Riot's README was about kernel-debuginfo dance steps.
+The old I/O Riot was Systemtap. Systemtap programs are translated into a kernel module against the running kernel's exact headers, and that module then has to be loaded with `insmod`. That meant the user has to install a kernel-debuginfo package matching their running kernel, and a fresh build per host (or per kernel update).
 
 CO-RE throws all of that out. The idea, in one paragraph: when you write a BPF program that reads `task->mm->start_stack`, you don't bake the offsets of those fields into the compiled program. Instead, the compiler emits relocation records ("at this instruction, fetch the offset of `mm` inside `task_struct`"). At load time, libbpf looks up the actual offsets in the target kernel's BTF (BPF Type Format, a description of every kernel struct embedded in `/sys/kernel/btf/vmlinux` on any modern kernel) and patches the program in place. The same `.bpf.o` that ran on a 5.10 Debian kernel runs on a 6.8 Fedora kernel without recompilation.
 
@@ -150,58 +190,52 @@ Old I/O Riot (Systemtap)                 New ior (libbpf + CO-RE)
   insmod / modprobe                         libbpf loader:
        │                                        │  • read /sys/kernel/btf/vmlinux
        ▼                                        │  • patch field offsets
-  attached, this kernel only                 │  • verify + load
-                                              ▼
+  attached, this kernel only                    │  • verify + load
+                                                ▼
                                           attached, runs anywhere
 ```
 
-What that buys ior in practice: I ship a single `ior` binary. On any Linux ≥4.18-ish with BTF available (which is almost all of them now — Debian, Ubuntu, Fedora, Arch, RHEL, and ElRepo's `kernel-ml` builds all ship `CONFIG_DEBUG_INFO_BTF=y` by default), it just works. No kernel-debuginfo dependency, no per-kernel build matrix, no DKMS hooks. The first time I tried `scp ior fedora-box:` and it ran without complaint after a 6-month gap I had to double-check it wasn't silently doing nothing.
-
 So the operational shape is: pick one box, do the install dance from the Rocky section above (or `docs/build-rocky-linux-9.md` for a native Fedora/RHEL build) once, build, then distribute the 23 MB binary wherever you want to trace. The build host needs Go and clang and the static libraries. The trace hosts need a BTF-enabled kernel and `sudo`. That's it.
 
-The runtime shape of a trace pipeline lines up with that:
+The whole "one build, every host" picture:
 
 ```
- kernel side                                userspace (this binary)
- ───────────                                ───────────────────────
-                                            ┌──────────────────────┐
-   tracepoint:                              │  Go process          │
-   sys_enter_openat                         │  ┌────────────────┐  │
-        │                                   │  │  aggregator    │  │
-        ▼                                   │  │  (latency,     │  │
-   ┌─────────┐                              │  │   stacks,      │  │
-   │ BPF prog│ ─── perf ring buf ──────────>│──│   filters)     │  │