Category: Tips

Symbolized stacktraces for a package in Debian

By default, Debian packages aren’t symbolized, resulting in unreadable stacktraces:

#0  0x00007fb9d7a3a774 in ?? ()
#1  0x00005574a4450ea0 in ?? ()
#2  0x00005574a42cea60 in ?? ()
#3  0x00005574a3f8bd20 in ?? ()
#4  0x00007ffe0d782200 in ?? ()

The first step is to determine the right package containing the debug symbols for your binary. This can be done using find-dbgsym-packages from the debian-goodies packages:

$ find-dbgsym-packages /usr/bin/gnome-control-center

Install the relevant *-dbgsym packages, for example:

$ sudo apt install gnome-control-center-dbgsym libglib2.0-0-dbgsym

And now you can have symbolized stacktrace:

#0  0x00007fb9d7a3a774 in g_type_check_instance_cast (type_instance=0x100000002, iface_type=93959409689392) at ../../../gobject/gtype.c:4122
#1  0x00005574a0d1382f in private_key_picker_helper (self=self@entry=0x5574a3f8bd20, filename=filename@entry=0x5574a42cea60 "*******************************************", changed=changed@entry=1)
    at ../panels/network/wireless-security/eap-method-tls.c:252
#2  0x00005574a0d13a34 in private_key_picker_file_set_cb (chooser=<optimized out>, user_data=0x5574a3f8bd20) at ../panels/network/wireless-security/eap-method-tls.c:297
#3  0x00007fb9d7a173b0 in g_closure_invoke (closure=0x5574a4302fb0, return_value=return_value@entry=0x0, n_param_values=2, param_values=param_values@entry=0x7ffe0d782200, invocation_hint=invocation_hint@entry=0x7ffe0d782180)
    at ../../../gobject/gclosure.c:832
#4  0x00007fb9d7a2a076 in signal_emit_unlocked_R (node=node@entry=0x5574a1335ba0, detail=detail@entry=1327, instance=instance@entry=0x5574a3f91350, emission_return=emission_return@entry=0x0, instance_and_params=instance_and_params@entry=0x7ffe0d782200)
    at ../../../gobject/gsignal.c:3796
#5  0x00007fb9d7a30bf5 in g_signal_emit_valist (instance=<optimized out>, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7ffe0d7823a0) at ../../../gobject/gsignal.c:3549

Further notes

By default, Debian doesn’t create core dumps. This can be changed (for the current running terminal session) with

$ ulimit -c unlimited

You can create more sensible core dump names using:

sudo sysctl -w kernel.core_pattern=/tmp/core-%e.%p.%h.%t

English interface on the Xiaomi AIoT AX3600 Router

Three years ago, I bought the Xiaomi AIoT AX3600 Router. Back at the time, only the Chinese version was available, and that one only supported Chinese as an interface language for the admin panel, which isn’t great. Time passed, and the international variant came out. Both versions have different firmwares, so the Chinese version remained pegged to the Chinese interface. Luckily, someone over at OpenWRT found out that you can install the internation firmware on the Chinese variant. The firmware is available over here.

$ sha256sum miwifi_r3600_all_6510e_3.0.22_INT.bin
67881cea85f8452bb63b3067d3100796a9c1b4f65aaa3479dcb4d01216bc6ce4  ./miwifi_r3600_all_6510e_3.0.22_INT.bin

Once you install it, you’ll have an option to change the language to English.

ls colors broken under Solarized dark theme

A recent change introduced in GNU coreutils changed the default dircolors for backup files to make them less conspicuous. However, despite having stated that it works on dark backgrounds, this change made it impossible to see backup files such as .tar, .swp, .bak, .old when using the dark variant of the Solarized color scheme of the terminal. It can be seen in the following screenshots:

Solarized dark
Solarized light

To fix it, we’ll override the colors by creating ~/.dircolors file:

$ dircolors -p | sed "s/00;90/00;30/g" > ~/.dircolors
$ eval $(dircolors -b ~/.dircolors)

This will set the color of backup files to black, which makes them not stand out, but still readable.

This is the bash function I used to pretty-print all ls colors:

( # Run in a subshell so it won't crash current color settings 
    dircolors -b >/dev/null
    IFS=:
    for ls_color in ${LS_COLORS[@]}; do # For all colors
        color=${ls_color##*=}
        ext=${ls_color%%=*}
        echo -en "\E[${color}m${ext}\E[0m " # echo color and extension
    done
    echo
)

Another option, albeit more verbose, would be

$ dircolors --print-ls-colors ~/.dircolors | paste -sd ''

Display reboot required message on Debian

You can use MOTD (message of the day) to let you know if a Debian server requires reboot and why upon login.

Create a new file named /etc/update-motd.d/98-reboot-required and add to it the following lines:

#!/bin/sh -e
#
# helper for update-motd

if [ -f /var/run/reboot-required ]; then
	echo "*** System restart required ***"
        cat /var/run/reboot-required.pkgs
fi

Make the file executable:

$ sudo chmod +x /etc/update-motd.d/98-reboot-required

Now, you can test the new MOTD script using:

$ run-parts --lsbsysinit /etc/update-motd.d

If you have any installed updates that require reboot, you will get a message stating so, with a list of the packages that require the reboot.

*** System restart required ***
linux-image-5.10.0-19-cloud-amd64

Rewriting EXIF tags in JPEGs

Some out-of-camera JPEGs have bad metadata that digiKam doesn’t parse correctly. The problematic photos have the same characteristics:

  1. In the Properties tab, there is no Photograph Properties section, instead digiKam has a digiKam Properties section with the caption set to None.
  2. In the Metadata tab, not metadata is shown under Exif. However, full details are available under Exiftool.

The solution is to rewrite the EXIF tags using exiftool. This fixes the bad metadata and allows digiKam to properly read the photo’s metadata.

exiftool -overwrite_original -all= -tagsfromfile @ -all:all *.JPG

For the files with bad EXIF metadata, the command will report the following warning:

Warning: [minor] Error reading PreviewImage from file - DSC06635.JPG

Connecting to WP2 Enterprise network with EAP-TLS authentication

Recently, I had to connect to a hidden WiFi network with an EAP-TLS authentication. When configured via the NetworkManager UI on Ubuntu, it would work. However, on Debian Unstable running Gnome 42 and on Arch, the same process didn’t work. The problem seems to be an empty configuration line for domain-suffix-match that gets created. To solve it, you can remove the domain-suffix-match using nmcli:

$ nmcli connection modify CorpSSID 802-1x.domain-suffix-match ""

Alternatively, you can configure the WiFi network directly with nmcli without setting the problematic property>:

nmcli connection add type wifi ifname wlp0s20f3 \
  con-name CorpSSID \
  802-11-wireless.ssid CorpSSID \
  802-11-wireless-security.key-mgmt wpa-eap \
  802-1x.eap tls \
  802-1x.identity guyru \
  802-1x.client-cert /absolute/path/wifi-certs/signed-certificate.cer \
  802-1x.private-key /absolute/path/wifi-certs/private.key

It’s important to have absolute paths to both the client certificate and the private key.