grep -rl "#debugging" ~/writing ~/notes
#debugging
1 post and 6 notes tagged debugging.
20261 post
- 9 min
Debugging a systemd service without guessing
A repeatable path from failed unit to useful evidence using systemctl, journalctl, exit status, and the unit's real runtime context.
Notes
- TIL
ldd may run the binary you are inspecting
ldd is not a parser. It is a shell script that asks the dynamic loader to trace itself — normally by running the loader with --list, and in some versions and…
- TIL
Core dumps are free until you need one
The kernel refuses to write core dumps by default (RLIMIT_CORE starts at 0), which is why production crashes usually leave nothing behind. systemd raises that…
- TIL
Find and kill the process using a TCP port
When a port is already in use, find who owns it before reaching for a reboot: ss -ltnp shows the PID in the users:(...) column (use sudo to see other users'…
- TIL
perf counts, perf samples — pick the right one
perf has two modes and they answer different questions. Decide which one you are asking before you collect anything. Count when the question is how much:…
- TIL
Deleted files can still fill a disk
When df says a filesystem is full but du can't find the space, a process is usually holding a deleted file open. The blocks aren't freed until the last file…
- TIL
Measure durations with the monotonic clock
Linux has several clocks, and mixing them up is a reliable way to ship a bug that only appears in production. CLOCK_REALTIME is the wall clock: NTP,…