Hi, I have an ERLite running 15.05.1 off the internal USB stick on 1 large ext4 partition.
As there are no ext4 LEDE images for the erlite, what is the best way to upgrade?
how much of flash memory you have in this router?
None. It runs entirely off the internal 4GB flash drive (connected via USB).
cool device 
in lede database is link to openwrt page.
Yes, but for OpenWrt, this image is built: openwrt-15.05.1-octeon-erlite-ext4-sysupgrade.tar
There are no ext4 LEDE images built for this device.
EdgeRouter-Lite
https://lede-project.org/toh/hwdata/ubiquiti/ubiquiti_edgerouter_lite
Is this what you want?
https://downloads.lede-project.org/releases/17.01.0/targets/octeon/generic/lede-17.01.0-r3205-59508e3-octeon-erlite-squashfs-sysupgrade.tar
No, that's the squashfs image. I'm looking for the ext4 image.
Same question here (in same configuration). Does LEDE project plan on building ext4 sysupgrade images? I'd prefer not to move to squashfs unless that's the only way going forward.
You don't want to use the 17.01.1 image as it appears to be broken! Following is a section of output from firstboot using https://downloads.lede-project.org/releases/17.01.1/targets/octeon/generic/lede-17.01.1-octeon-erlite-squashfs-sysupgrade.tar
[ 14.491661] mount_root: rootdisk overlay filesystem has not been formatted yet
F2FS-tools: mkfs.f2fs Ver: 1.8.0 (2017-02-03)
Info: Debug level = 0
Info: Label = rootfs_data
Info: Trim is enabled
Info: Segments per section = 1
Info: Sections per zone = 1
Info: sector size = 512
Info: total sectors = 28639360 (13984 MB)
Info: zone aligned segment0 blkaddr: 512
Info: format version with
"Linux version 4.4.61 (buildbot@builds-02.infra.lede-project.org) (gcc version 5.4.0 (LEDE GCC 5.4.0 r3103-1b51a49) ) #0 SMP Sat Apr 15 16:13:45 2017"
Info: [/dev/loop0] Discarding device
Info: This device doesn't support BLKSECDISCARD
Info: This device doesn't support BLKDISCARD
Info: Overprovision ratio = 1.700%
Info: Overprovision segments = 240 (GC reserved = 125)
Info: format successful
[ 26.136471] mount_root: unable to set filesystem state
[ 26.142073] mount_root: switching to f2fs overlay
[ 26.149011] overlayfs: failed to resolve '/overlay/upper': -5
[ 26.155488] mount_root: mount failed: No such device, options lowerdir=/,upperdir=/overlay/upper,workdir=/overlay/work
[ 26.166397] mount_root: switching to f2fs failed - fallback to ramoverlay
[ 26.243409] urandom-seed: Seed file not found (/etc/urandom.seed)
Since the overlayfs is not mounted properly modifications to the configuration are not able to be saved after a reboot.
The 17.01.0 release doesn't have this issue and the result is a 16GB Flash disk with a 13.7 GB loop mounted f2fs filesystem.
I ended up just moving to squashfs / overlayfs on mine and just redoing the install from scratch. My config is pretty simple and enough seems to have changed since openwrt for me to just rebuild it from scratch.
I did hit the same problem as @RaylynnKnight did with 17.01.1, and I think I stumbled on the solution:
I ended up repartitioning my usb stick with a smaller second partition, and then rewriting the squashfs image on top of it. With that, it actually set up the filesystem correctly and then I was able to grow the ext4 fs into the remaining space post-install. No idea why that worked however. I didn't save the logs.