How to Find Which Process Is Listening on a Port in Linux
Check TCP and UDP via ss, analyze the binding address, and distinguish a local listening socket from service availability from the internet.
Альбина
3 minViews10
GENERAL IT · JOURNAL
Technology in practice
Ideas, experience and solutions for your project.
File Deleted but Space Not Freed: Diagnostics with lsof
How to find an open deleted file using lsof and verify space reclamation. A real test with two file descriptors: why du decreases immediately, but available space reported by df only grows after the last FD is closed.
Альбина
6 minViews7
Disk is lagging: how to read iostat without universal thresholds
We examine latency, queue depth, and I/O operations, accounting for SSDs, virtual disks, and the difference between the first report and subsequent intervals.
Альбина
3 minViews2
How to Check MySQL Connectivity Without Confusing Availability with Permissions
We test connection, login, and table reading separately. A real MySQL 8.0.46 testbed demonstrates the differences between errors 2003, 1045, and 1142, as well as a successful ping.
Альбина
7 minViews16
How to Verify File Integrity Using SHA-256
We compare the checksum of a downloaded archive against a trusted value and explain what this verification proves and what it does not confirm.
Альбина
3 minViews15
Permission Denied: How to Find the Problem in the Path and Access Rights
Use namei and stat to check the entire file path, owner, and access mode before changing the site directory permissions.
Альбина
3 minViews6
Incorrect Server Time: Checking Clocks and Synchronization
How to use timedatectl to distinguish between a time zone error and clock desynchronization, and gather data before manually adjusting the time.
Альбина
3 minViews10
How to Measure Website Response Time with curl: Codes, Redirects, and Timing
A quick HTTP check with a timeout: distinguish connection errors from server responses and do not treat cumulative timings as independent stages.
Альбина
3 minViews5
Why dig and the app see different addresses: checking resolvectl
How to view DNS servers and name resolution rules in a systemd-resolved system, especially with VPNs and multiple network interfaces.
Альбина
3 minViews3
How to Check a DNS Record with dig and Read the Response Correctly
How to read a dig DNS response: real examples of NOERROR with addresses, empty NODATA responses, and NXDOMAIN. Status, TTL, and the next verification step without changing the network.
Альбина
6 minViews3
How to Check Server IP Addresses and Routes Without Changing the Network
Quick diagnostics with ip: interfaces, addresses, and the selected route to the recipient. Helps gather facts without risking loss of remote access.
Альбина
3 minViews6
Scheduled Task Did Not Run: Checking the systemd Timer
How to link a timer to the service it launches, verify past and next executions, and avoid mistaking an active timer for a successful task.
Альбина
3 minViews2
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