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RT-AC5300 failed to write /var/lib/misc/dnsmasq.leases: No space left on device

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Hello, first-time poster here. I found similar topics, but they were all under the Merlin category, and it's not clear to me that they have the same cause, as those users may have been running other scripts.

I am running an RT-AC5300 on stock firmware. We bought it years ago when the model was new, have kept the stock Asus firmware updated, and it has always worked fine for us. For the past few weeks, we have been having connection issues across various devices. It always seems to be that a few devices can connect, but not all simultaneously. Which devices can connect changes. Sometimes the connections fail outright, other times the clients receive bogus subnets and IPs. I finally checked the logs today, and saw a bunch of messages like this:

Jul 18 20:13:20 dnsmasq[404]: failed to allocate 124 bytes
Jul 18 20:13:20 dnsmasq-dhcp[404]: failed to write /var/lib/misc/dnsmasq.leases: No space left on device (retry in 60s)

Seeing as how we're running stock firmware, this seems like a blatant design flaw, but I disabled all the logging, traffic analysis, QoS, etc., cleared whichever logs I could from the web GUI, rebooted the router, and it seemed to work fine for a while. Later in the day, I started seeing the same messages again.

At this point, I'm thinking of just factory-resetting the thing. We don't have much in the way of custom configuration aside from a non-default gateway IP, so it wouldn't be too much of a hassle. I just wanted to post here first to see if anyone had any idea what might be causing it. I saw some posts about swap files and USB devices, but again, I'm running stock firmware and don't think they should be relevant to our situation unless there's a serious bug in the Asus firmware. I'm also wondering if it's worth running Merlin. I have yet to confirm, but I saw a post that suggested you can just SSH in and manually free storage. Ideally, factory-resetting should do that, but I obviously won't know until I try it or hear from someone with experience.

Any help is appreciated!


After doing some more searching, I stumbled upon another forum post (different site) that linked to this notice:


Whether that's what happened to my device or not, I have no idea, but the timing of the announcement more or less coincides with when I started seeing issues, so I figured it was at least a possibility. I factory-reset the router from the Administration menu in the web GUI, and it seems to be working okay for now. That's what I thought last time though, so we'll see. I'll update this post if anything changes.
Last edited:
Your router has run out of memory, which in turn is causing the client connection problem. As this wasn't a problem in the past it's probably either a bug in the current firmware, or a problem with the bad ASD update that you linked to.

Follow the instructions in that link. You might want to do step 2 in any case - Save your settings (Administration - Restore/Save/Upload Setting), perform a hard reset, and then reload your settings.


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