How to Clear Apache Cache

What “Apache cache” can mean

Apache itself does not have a single button. Caching usually comes from mod_cache with mod_cache_disk (files under a CacheRoot) or mod_cache_socache (shared memory / memcached backends). Separate layers—PHP OPcache, FastCGI app caches, reverse proxies in front of httpd, and browser/CDN caches—are not cleared by trimming mod_cache alone.

Disk cache (mod_cache_disk)

Identify CacheRoot and structure from your config (CacheDirLevels / CacheDirLength). Prefer htcacheclean to enforce maximum disk/inode usage rather than rm -rf on the whole tree during traffic—deleting files an active worker still maps can cause errors. Run apachectl configtest before reloads.

Step	Action	Watch for
Measure	`du -sh` / `df -i` on CacheRoot	Inode exhaustion before bytes
Trim	`htcacheclean` daemon or cron with limits	Path must match vhost cache config
Reload	`apachectl graceful` / `systemctl reload httpd`	In-flight downloads; RAM caches drop on child recycle

Shared-object cache (mod_cache_socache)

Entries live in the configured socache provider (for example shmcb paths or memcached). Clearing often means restarting the provider, flushing the remote store, or shortening TTLs—consult the provider docs. Do not assume on-disk paths cover socache RAM.

After you clear

Expect an origin load spike as misses refetch. Pre-warm critical URLs from a canary or load test account. If HTML is correct but assets look old, purge nginx edge cache or CDN separately.

Frequently Asked Questions

Q.Does apachectl restart clear mod_cache_disk files?

No—a restart recycles workers but leaves files under CacheRoot until htcacheclean or expiry removes them. Use htcacheclean or controlled deletion aligned with maintenance windows.

Q.Is it safe to rm -rf the entire CacheRoot?

Risky under load: workers may still serve or write entries. Prefer htcacheclean limits, or stop traffic / quiesce the vhost, then remove, then reload—document the blast radius.

Q.Why do users still see stale content after clearing Apache cache?

Browser cache, CDN, downstream reverse proxy, or PHP OPcache may still hold responses. Verify with curl -H 'Cache-Control: no-cache' directly to the origin and compare headers.

Q.What is htcacheclean used for?

It prunes mod_cache_disk directories to stay under configured disk or inode limits—safer than ad-hoc deletes for long-running production caches.

Q.How do I disable caching temporarily?

Use CacheDisable for a path or comment CacheEnable blocks after configtest, then graceful reload—faster for incidents than bulk deleting cache files mid-request.

Q.Does mod_cache_socache clear when I reload httpd?

shmcb-backed segments often persist across graceful reload depending on layout; memcached entries persist until TTL or explicit flush. Check your provider and MPM settings.

Q.Will clearing cache spike load on my origin?

Yes—cold caches increase backend requests. Schedule during low traffic or pre-warm; use stale-while-revalidate style headers at the edge where possible.

Q.Where is CacheRoot configured?

In your Apache config or included snippets—search for CacheRoot and CacheDirLevels. Align htcacheclean paths exactly; a typo silently cleans the wrong directory.