My Archer C7 v1.1 looks like it has 2-4MB flash mem instead of 8MB

stormed_labastille · March 18, 2024, 12:04am

Hi, I'm having trouble with my TP-Link Archer C7 AC1750 v1.1, it looks like it only has 2-4MB flash memory left:

root@OpenWrt:~# df -m
Filesystem           1M-blocks      Used Available Use% Mounted on
/dev/root                    4         4         0 100% /rom
tmpfs                       60         0        60   0% /tmp
/dev/mtdblock4               2         0         2  11% /overlay
overlayfs:/overlay           2         0         2  11% /
tmpfs                        1         0         1   0% /dev

(That output is directly after firstboot -y && reboot running on 23.05.2)
/rom says size=4MB, /overlay only has 2MB. I don't know if this is expected, the hardware description here says flash memory = 8MB, but I'm not sure if the full 8MB is supposed to show up above.

The Luci interface under Status -> Storage -> Disk space says 2.06MB

root@OpenWrt:~# dmesg | egrep "jffs|overlay"
[    0.000000] Kernel command line: console=ttyS0,115200n8 rootfstype=squashfs,jffs2
[    0.261858] jffs2: version 2.2 (NAND) (SUMMARY) (LZMA) (RTIME) (CMODE_PRIORITY) (c) 2001-2006 Red Hat, Inc.
[    9.728600] jffs2: notice: (437) jffs2_build_xattr_subsystem: complete building xattr subsystem, 13 of xdatum (0 unchecked, 4 orphan) and 17 of xref $
[    9.746103] mount_root: switching to jffs2 overlay
[    9.756891] overlayfs: upper fs does not support tmpfile.

I can't install the package I want:

Installing openssl-util (3.0.13-1) to root...
Collected errors:
 * verify_pkg_installable: Only have 1344kb available on filesystem /overlay, pkg libopenssl3 needs 1411
 * opkg_install_cmd: Cannot install package openssl-util.

Is there hope for installing that package or is it time to buy a new device?

psherman · March 18, 2024, 12:11am

https://openwrt.org/faq/no_space_left_on_device

stormed_labastille · March 18, 2024, 12:15am

Hi, thanks for the link, the extroot suggestion seems to require 8MB flash. Do you know how I can check whether the device is functioning correctly, i.e. what command should show the documented 8MB instead of the 2&4 that I see in df ?

psherman · March 18, 2024, 12:53am

I prefer using df -h as it gives. bit more resolution into the actual usage, while also making it human readable (that's the -h argument).

root@OpenWrt:~# df -m
Filesystem           1M-blocks      Used Available Use% Mounted on
/dev/root                    4         4         0 100% /rom
tmpfs                       28         0        28   0% /tmp
/dev/mtdblock5               2         0         2  13% /overlay
overlayfs:/overlay           2         0         2  13% /
tmpfs                        1         0         1   0% /dev
root@OpenWrt:~# df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/root                 3.8M      3.8M         0 100% /rom
tmpfs                    28.0M     64.0K     28.0M   0% /tmp
/dev/mtdblock5            1.9M    240.0K      1.6M  13% /overlay
overlayfs:/overlay        1.9M    240.0K      1.6M  13% /
tmpfs                   512.0K         0    512.0K   0% /dev

You should be able to install the required extroot packages within the 8MB total footprint. I've done it many times. Alternatively, you can use the image builder to pre-install them, saving some space in the process.

Nothing is wrong with your device -- the above is from another 8M device (Linksys E3000)

slh · March 18, 2024, 3:59am

There is one very simple -approximate- way to check this, take a look at the size of the provided sysupgrade image.

In this case, the archer c7-v1 sysupgrade image for 23.05.2 weighs 5888.3 KB, keep in mind that bootloader+bootloader_env and ART weigh another 196 KB (or more on other devices), now how much free space can you expect after installing OpenWrt on a 8 MB flash device?

--
Yes, some vendors come with a rather wasteful flash partitioning and/ or dual-firmware setups, but a) neither is the case here, b) it still gives you an upper ceiling to refine your calculations.

frollic · March 18, 2024, 5:18am

Another option is to skip the webui in the main image, establish extroot, then install it once it's working.

stormed_labastille · March 18, 2024, 3:27pm

Thanks! I saw this page on flash layouts, and executed some commands on my device that indeed seem to confirm the 8MiB flash presence:

root@OpenWrt:~# opkg install fdisk lsblk
...
root@OpenWrt:~# df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/root                 3.8M      3.8M         0 100% /rom
tmpfs                    59.6M   1008.0K     58.6M   2% /tmp
/dev/mtdblock4            2.1M   1020.0K      1.1M  48% /overlay
overlayfs:/overlay        2.1M   1020.0K      1.1M  48% /
tmpfs                   512.0K         0    512.0K   0% /dev
root@OpenWrt:~# fdisk -l | grep Disk
Disk /dev/mtdblock0: 128 KiB, 131072 bytes, 256 sectors
Disk /dev/mtdblock1: 7.81 MiB, 8192000 bytes, 16000 sectors
Disk /dev/mtdblock2: 2.22 MiB, 2330112 bytes, 4551 sectors
Disk /dev/mtdblock3: 5.59 MiB, 5861376 bytes, 11448 sectors
Disk /dev/mtdblock4: 2.06 MiB, 2162688 bytes, 4224 sectors
Disk /dev/mtdblock5: 64 KiB, 65536 bytes, 128 sectors
root@OpenWrt:~# lsblk
NAME      MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
mtdblock0  31:0    0  128K  1 disk
mtdblock1  31:1    0  7.8M  0 disk
mtdblock2  31:2    0  2.2M  1 disk
mtdblock3  31:3    0  5.6M  1 disk /rom
mtdblock4  31:4    0  2.1M  0 disk /overlay
mtdblock5  31:5    0   64K  1 disk
root@OpenWrt:~# cat /proc/mtd
dev:    size   erasesize  name
mtd0: 00020000 00010000 "u-boot"
mtd1: 007d0000 00010000 "firmware"
mtd2: 00238ed3 00010000 "kernel"
mtd3: 0059712c 00010000 "rootfs"
mtd4: 00210000 00010000 "rootfs_data"
mtd5: 00010000 00010000 "art"
root@OpenWrt:~# dmesg | grep '0\.4[1-9]'
[    0.411683] Creating 3 MTD partitions on "spi0.0":
[    0.416559] 0x000000000000-0x000000020000 : "u-boot"
[    0.427086] 0x000000020000-0x0000007f0000 : "firmware"
[    0.433639] 2 tplink-fw partitions found on MTD device firmware
[    0.439713] Creating 2 MTD partitions on "firmware":
[    0.444753] 0x000000000000-0x000000238ed3 : "kernel"
[    0.449803] mtd: partition "kernel" doesn't end on an erase/write block -- force read-only
[    0.460548] 0x000000238ed4-0x0000007d0000 : "rootfs"
[    0.465605] mtd: partition "rootfs" doesn't start on an erase/write block boundary -- force read-only
[    0.475856] mtd: setting mtd3 (rootfs) as root device
[    0.481866] 1 squashfs-split partitions found on MTD device rootfs
[    0.488167] 0x0000005c0000-0x0000007d0000 : "rootfs_data"
[    0.494586] 0x0000007f0000-0x000000800000 : "art"

This leads me to speculate that the 8MiB = 8192 KiB flash of the device is divided as follows:

 8192
 ├── 128          u-boot      mtd0
 ├── 8000         firmware    mtd1
 │   ├── 2275.5   kernel      mtd2
 │   └── 5724     rootfs      mtd3
 │       ├── 2112 rootfs_data mtd4 /overlay, /
 │       └── 3612 -           -    /rom
 └── 64           art         mtd5

I'm not sure about the interpretation of the /rom mount mentioned in df -h, as corresponding to mtd3 minus mtd4, is that the way I should read it? 3612 KiB = 3698688 bytes = 3.7M. That doesn't exactly match the 3.8M that df -h displays, but seems to be the best guess for now. Is that how the /rom mount of /dev/root should be seen as part of flash memory?

frollic · March 18, 2024, 3:32pm

It's all part of the flash memory.

stormed_labastille · March 18, 2024, 3:35pm

Yes that's clear, I'm just wondering if /rom = mtd3 minus mtd4, and if so where the difference of 3.8M with 3.7M comes from.

brada4 · June 12, 2024, 9:07am

https://openwrt.org/toh/tp-link/archer_c7#hardware_highlights

Device has 8MB flash, zero if you round to closest terabyte