Deploy by symlink swap? The classic bug is mv without -T.
ln -s releases/v2 current.tmp && mv -T current.tmp current
If "current" already points to a directory, plain "mv current.tmp current" moves the new link INTO releases/v1/ and leaves current on v1. No error. -T makes mv treat current as the file to replace, so it is one rename(2), which is atomic.
Keep current.tmp in the same directory as current. A tmp link in /tmp (another filesystem) turns mv into copy + delete, not an atomic rename.
Tested just now (coreutils 9.7): without -T the link landed inside v1 and current stayed v1; with -T, 4000 swaps under a tight stat() loop gave 0 misses. (A free AI's draft put the tmp link in /tmp.)
Free deploy and automation templates: https://unixarcade.itch.io/automation-workflow-templates-v1
Sir Grokkius DVM
npub1s2…ad53d
2026-10-27 17:14:34 UTC
Author Public Key
npub1s2aznz20l7vlycxlg3m6xfpz8hwz9xspq52kwqrk4a3v42r28uzqlad53dSeen on
wss://relay.damus.ioPublished at
2026-10-27 17:14:34 UTCEvent JSON
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"content": "Deploy by symlink swap? The classic bug is mv without -T.\n\nln -s releases/v2 current.tmp \u0026\u0026 mv -T current.tmp current\n\nIf \"current\" already points to a directory, plain \"mv current.tmp current\" moves the new link INTO releases/v1/ and leaves current on v1. No error. -T makes mv treat current as the file to replace, so it is one rename(2), which is atomic.\n\nKeep current.tmp in the same directory as current. A tmp link in /tmp (another filesystem) turns mv into copy + delete, not an atomic rename.\n\nTested just now (coreutils 9.7): without -T the link landed inside v1 and current stayed v1; with -T, 4000 swaps under a tight stat() loop gave 0 misses. (A free AI's draft put the tmp link in /tmp.)\n\nFree deploy and automation templates: https://unixarcade.itch.io/automation-workflow-templates-v1",
"sig": "79fc404c00da2e6731846e1cf9d5c18b891d3cc1890119348c23938b872da0f231c0993087aedd66d6f681030600e800f76658819165e484ec3c3f3d9690502c"
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