# Xtrabackup: Error writing file '\<unopen fd\>' (os errno 5 - input/output error)

**URL:** <https://forums.percona.com/t/xtrabackup-error-writing-file-unopen-fd-os-errno-5-input-output-error/23094>\
**Category:** Percona XtraBackup\
**Created:** [June 25, 2023, 1:43pm UTC](https://forums.percona.com/t/xtrabackup-error-writing-file-unopen-fd-os-errno-5-input-output-error/23094 "2023-06-25T13:43:46Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![bili](https://avatars.discourse-cdn.com/v4/letter/b/e9a140/32.png) [@bili](https://forums.percona.com/u/bili)\
**Post date:** [June 25, 2023, 1:43pm UTC](https://forums.percona.com/t/xtrabackup-error-writing-file-unopen-fd-os-errno-5-input-output-error/23094/1 "2023-06-25T13:43:46Z")

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hello, Please tell me what is the cause of this problem…

mysql：8.0.26  
xtrabackup：8.0.27

fullbackup

xtrabackup: Error writing file ‘’ (os errno 5 - input/output error)  
xtrabackup：Error：xtrabackup\_copy\_datafile() failed.  
xtrabackup：Error：failed to copy datafile.

ulimit -n  
1000000

 ![IMG_0505](https://us1.discourse-cdn.com/flex019/uploads/percona1/original/2X/0/04ccf466424eced2fc1f7d4676c6a354471ff854.jpeg)

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**Author:** ![kedarpercona](https://sea1.discourse-cdn.com/flex019/user_avatar/forums.percona.com/kedarpercona/32/809_2.png) [@kedarpercona](https://forums.percona.com/u/kedarpercona)\
**Post date:** [June 25, 2023, 2:17pm UTC](https://forums.percona.com/t/xtrabackup-error-writing-file-unopen-fd-os-errno-5-input-output-error/23094/2 "2023-06-25T14:17:55Z")

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Welcome to the Percona community @bili,

To start with I’d consider using exact version for xtrabackup and mysql.  
Then, I assume here that the `ulimit -n 1000000` is for the user you run xtrabackup with. If not, I’d make sure of that.  
Now, can you confirm if the command did progress for some time and then failed or was it an immediate failure? I’m trying to figure out if the issue is with the permissions/storage etc which might not let the backup to even start OR is it some limitation that is causing to terminate after it started!

There’s a “similar” issue that was noted [here](https://forums.percona.com/t/xtrabackup-8-0-4-prepare-fails-with-linux-os-errors), does it help?

Thanks,  
K.

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<div class="post-metadata">

**Author:** ![bili](https://avatars.discourse-cdn.com/v4/letter/b/e9a140/32.png) [@bili](https://forums.percona.com/u/bili)\
**Post date:** [June 26, 2023, 2:07am UTC](https://forums.percona.com/t/xtrabackup-error-writing-file-unopen-fd-os-errno-5-input-output-error/23094/4 "2023-06-26T02:07:24Z")

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Thanks for answering my question. The command did progress for some time and then failed. It may be a storage issue and high storage usage. I’ll check again. Thanks！

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**Author:** ![cnnsndnsqu](https://avatars.discourse-cdn.com/v4/letter/c/f475e1/32.png) [@cnnsndnsqu](https://forums.percona.com/u/cnnsndnsqu)\
**Post date:** [December 13, 2023, 2:13pm UTC](https://forums.percona.com/t/xtrabackup-error-writing-file-unopen-fd-os-errno-5-input-output-error/23094/5 "2023-12-13T14:13:14Z")

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Thanks for the information!