OpenWrt on 4/32 devices

You have a device with 4MB flash and/or 32MB RAM.
You have read and understood the 4/32 warning.
You have adjusted your expectations according to this warning.
You still want to install OpenWrt on your 4/32 device for

• training purposes only (soldering, OpenWrt, Linux in general); if it breaks, it breaks, it's no loss.
• basic, low level routing functions only

Now you are asking: What can I do?

Find answers below.

See also Security for the latest and fully supported OpenWrt version.

Choose the OpenWrt version according to your needs for maintenance releases and security fixes.

• 15.05
  • No. EoL, unmaintained, no security fixes since 2016. Don't even think about it.
• 17.01
  • No. EoL, unmaintained. Has known security flaws as of November 2019 that will not be patched.
• 18.06
  • No. EoL, unmaintained.
• 19.07
  • No. EoL, unmaintained.
  • Offers “ath79” target as “ar71xx” target has been deprecated
• 21.02
  • No. EoL, unmaintained.
  • Not likely viable for 4 MB flash devices
• 22.03
  • Not likely viable for 4 MB flash devices

How can I work around the 4 MB flash issue?

• build your own image 18.06/19.07 image with all possible space saving measures, or...
• ...use extroot (only if USB available)
  • no flash problems any more
  • “infinite”¹⁾ storage space available
  • install all the packages of the world, if you like
  • BUT: It's kind of pointless to have a bunch of large packages (VPN, etc.) stored in extroot, but no RAM to run them on.

Why should I build my own image rather than installing packages?

Building your own image compresses the packages you need to about half the size compared to installing them after you flash.

How can I work around the 32 MB RAM issue?

• Don't use LuCI (will not work at all, or will be terribly slow, or will crash due to OOM)
• Don't use RAM hungry applications (will not work at all, or will be terribly slow, or will crash due to OOM)

• https://forum.openwrt.org/t/installing-latest-openwrt-on-old-hardware/40031?u=tmomas
• https://forum.openwrt.org/t/installing-latest-openwrt-on-old-hardware/40031/5?u=tmomas

4/32 devices can be used with the latest versions ²⁾ mostly OK, provided that only basic routing functions are used.
I am using three of these devices: MR3040v2, tl-841v9 and tl-1043ndv1 on 19.07 build.

• https://forum.openwrt.org/t/installing-latest-openwrt-on-old-hardware/40031/8?u=tmomas

You're definitely looking at a custom build, but it can work for basic stuff. This is simpler than using extroot, which has the problem that the filesystem driver etc still must be in internal flash. Also its kind of pointless to have a bunch of large packages (VPN, etc.) stored in extroot but no RAM to run them on.

• Community builds in the OpenWrt forum - Search here for community builds for 4/32 devices
• OpenWrt 21.02.x Builds for ath79
• OpenWrt 19.07 Builds for TL-WR740N TL-WR741N TL-WR743ND TL-WR802N TL-WR840N TL-WR841N(D) TL-WR843N(D) TL-WR847N TL-WR940N TL-WR941ND
• OpenWrt 18.06.4 Build for TL-WR740N TL-WR741N TL-WR743ND TL-WR841N(D) TL-WR940N TL-WR941ND
• Custom Builds LEDE 17.01.7 & libreCMC v1.4.5 for TP-LINK WR740N(D) WR741N(D) WR841N(D) WR941N/D) All Versions
• Custom Builds LEDE 17.01.6 for TP-LINK WR841N(D) WR941N(D) WR743N(D) WR741N(D) WR740N(D) All Versions
• [Testing] LEDE 17.01 security backports for 4/32 devices
• Optimized build LEDE 17.01 / OpenWrt 18.06 / libreCMC for "small devices" TP-LINK WR740N(D) WR741N(D) WR743N(D) WR841N/D) All Versions