Software Testing is an Art!

MOBILE

Getting Android Logs

by  • 

Log-File locations

There are several directories where logs (including those from crashes) might appear – not all of them are standardized (i.e. some may be ROM-specific). Some examples are:

  • /data/anr “Application Not Responding” files
  • /data/dontpanic seems to be a standard location (AOSP), and contains some crash logs including traces
  • /data/kernelpanics
  • /data/panic/panic_daemon.config may point to other locations configured
  • /data/panicreports
  • /data/tombstones may hold several tombstone_nn files (with nn being a serial, increased with every new file). As tombstones are placed for the dead, it is done here for “processes died by accident” (i.e. crashed) – and it is what is referred to as “core dumps” on Linux/Unix systems. However, not all apps create tombstones; this must be explicitly enabled by the developer.

There may be some more locations, but as most logging is done on tmpfs  (tmpfs is a common name for a temporary file storage facility on many Unix-like operating systems)

 

Log commands to use with a terminal app (or adb)

We  are able re-direct them to a file (> filename.ext) or pipe them through a filter (| grep search-for-this):


1. Kernel log

dmesg
Run dmesg from adb to get a live output of the Android kernel logs (just like a logcat shows live output of the system logs).

The kernel logs are important for troubleshooting hardware issues and other low level issues.
It doesn’t require filtering like a logcat, since it is a smaller log. Works without root.

$ dmesg
<6>[82839.126586] PM: Syncing filesystems ... done.
<7>[82839.189056] PM: Preparing system for mem sleep
<4>[82839.189361] Freezing user space processes ... (elapsed 0.05 seconds) done.
<4>[82839.240661] Freezing remaining freezable tasks ... (elapsed 0.00 seconds) done.
<snip>

last kmsg
When the Android kernel crashes, it writes logs to last_kmsg.
This is like the last words of your Android device before it passes out. Android writes a quick log to last_kmsg before it reboots. last_kmsg helps to understand the reason of the issue.
There are a few other situations where Android writes to this log, such as kernel panics.

Right after force reboot, connect to  ADB, and run:

adb shell cat /proc/last_kmsg > last_kmsg.txt

The last_kmsg log it only written to when a failure causes a crash, random reboot, or kernel panic (or a couple other things). It doesn’t always exist.


2. Logcat

Can e.g. specify what area you are interested in — radio, events, etc.

# logcat -b events
I/am_create_service( 3457): [1085416560,nitro.phonestats/.widget.WidgetProvider4x1$WidgetUpdateService4x1,,3721]
I/am_destroy_service( 3457): [1085416560,nitro.phonestats/.widget.WidgetProvider4x1$WidgetUpdateService4x1,3721]
I/notification_cancel( 3457): [nitro.phonestats,4,0] 
<snip>


3. Getting device info

And tons of it: Device specifics, account information, services…

$ dumpsys
Currently running services:
  LocationProxyService
  SurfaceFlinger
  accessibility
  account
  activity
<snip>
DUMP OF SERVICE account:
Accounts:
  1 Account {name=xxxxxxx@googlemail.com, type=com.google}
<snip> 

$ dumpstate
========================================================
== dumpstate: 2012-08-18 23:39:53
========================================================

Build: Gingerbread GWK74 - CyanogenMilestone2
Bootloader: 0x0000
 
Radio: unknown <snip> ------ MEMORY INFO (/proc/meminfo) ------ MemTotal: 487344 kB MemFree: 10436 kB <snip>

 

4. All-in-One = 1+2+3 =  Bugreport

Make a big ball with everything together, from logcat to dumpstate:

$ bugreport > /mnt/sdcard/bugreport.txt

P.S.: Access to those information may require root.

Comments are closed.