# Application Update(.deb)

**URL:** <https://hub.mender.io/t/application-update-deb/3284>\
**Category:** Update Modules\
**Tags:** raspberry-pi-3\
**Created:** [March 2, 2021, 6:46am UTC](https://hub.mender.io/t/application-update-deb/3284 "2021-03-02T06:46:27Z")\
**Posts on this page:** 1\
**Showing post:** 13

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**Author:** ![drewmoseley](https://yyz2.discourse-cdn.com/flex036/user_avatar/hub.mender.io/drewmoseley/32/47_2.png) [@drewmoseley](https://hub.mender.io/u/drewmoseley)\
**Post date:** [March 17, 2021, 5:52pm UTC](https://hub.mender.io/t/application-update-deb/3284/13 "2021-03-17T17:52:05Z")

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If your root filesystem is readonly then you will indeed be unable to do application or file updates.

I’m not sure what you mean that ‘Memory A/B and Partial Update makes rootfs to be “readonly”’. That should not be the case. Doing an A/B update should not change your rootfs to be readonly.

Now, if you are referring to [robust binary delta updates](https://hub.mender.io/t/robust-delta-update-rootfs/1144/10), then indeed it is required that the root filesystem be readonly. This is to ensure that the contents of the filesystem have not changed. If it _has_ changed, then you will not be able to apply the binary delta. This does imply that you cannot use application or file updates in a system that _also_ uses binary delta updates.

Drew

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