How to Check Database Size and Largest Tables in MySQL 8.0
Diagnostic SELECT queries against INFORMATION_SCHEMA to estimate database, data, and index sizes in MySQL 8.0, with an explanation of InnoDB limitations.
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5 minViews8
GENERAL IT · JOURNAL
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Practical tips and verified solutions for Linux, servers and websites.
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How to Distinguish Memory Shortage from Standard Linux Cache
Check available memory and swap usage with free and vmstat to avoid mistaking useful file cache for a leak.
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3 minViews3
How to Check Certificate Expiry and HTTPS Chain via OpenSSL
We separately verify the local certificate and what the server actually serves: validity period, hostname, and chain trust require distinct checks.
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3 minViews9
How to Check the Installed Package Version and Update Source in Ubuntu
We verify the package using dpkg-query and apt-cache policy, distinguishing between the installed version, the candidate for update, and the actual source of the running process.
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3 minViews13
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.
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3 minViews10
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.
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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.
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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.
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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.
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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.
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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.
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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.
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3 minViews5
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