/data/logs/modemcrash is huge and growing I have a hitherto unmodified ZenFone 2.  Lately I've been constantly running low on space, and it's not my files -- it's that mysterious black hole: "system data".  As soon as I delete more apps &amp; my own data, it starts filling up the available space.

I finally rooted my phone, and found the culprit:
/data/logs/modemcrash
It currently has about 260 .tar.gz files (plus another 78 files in the "mmgr2" subdirectory) from the last 4 weeks or so, taking up 7GB, so nearly 2GB a day.  

I downloaded a 600kB archive, and it showed a 101MB file, suggesting a compression of nearly 200:1, but I extracted it and it stopped after 16MB with an error. Examination suggests that most of the data is from core dumps.

Sure I can delete them to temporarily recover the space, but... any ideas on how to prevent the problem from occurring?  I suppose I might be able to write-protect the directory, but it would be nice to ether solve the problem that's causing the crashes, or at least tell it to stop saving core dumps.



Some init*rc contents (none of the files have had datestamp changed from 1/1/1970 0:00 UTC):

/etc/init.rc:

    # Android default init.rc (system/core/rootdir/init.rc) should be untouched.
# *EXCEPTIONALLY*, definitions from Android default init.rc may be modified.
#
# Use this file for overrides prior to default init.rc definitions.
# Please keep this file to the bare minimum as default init.rc should be
# preferred to duplicates here.

### Import ###
# import Android default init.rc renamed init.aosp.rc
# init.aosp.rc actually gets parsed after all the content of this file.
import /init.aosp.rc


### Services ###
# Android init only keeps the first definition found for a service.
# Override a service from Android default init.rc by adding it here.

service media /system/bin/mediaserver
    class main
    user media
    group audio camera inet net_bt net_bt_admin net_bw_acct drmrpc mediadrm radio system
    ioprio rt 4

service keystore /system/bin/keystore /data/misc/keystore
    class main
    user keystore
    group keystore drmrpc system

service flash_recovery /system/bin/install-recovery.sh
    class main
    seclabel u:r:install_recovery:s0
    oneshot
root@Z00A_1:/etc # 


/etc/init.asop.rc:
(doesn't exist)

/etc/init.debug.rc:

# Enable by default android java wakelock logging
on init
#    mkdir /logs
    symlink /data/logs /logs
    write /proc/sys/kernel/kptr_restrict 2

on early-boot
    chown system log /logs
    chmod 0770 /logs

on post-fs-data
    mkdir /data/tombstones 0755 system system
    mkdir /data/system/    0755 system system
    mkdir /data/system/dropbox 0700 system system
    mkdir /logs/modemcrash 0775 system system
    mkdir /logs/aplogs 0775 system log

on charger
    # basic networking for "adb root"
    ifup lo
    hostname localhost
    domainname localdomain
    mount ext4 /dev/block/mmcblk0p7 /logs nosuid nodev barrier=1,data=ordered
    mkdir /logs/modemcrash 0775 system system
    mkdir /logs/aplogs 0775 system log

on ramconsole
    powerctl reboot

# crash and log services
#service crashlogd /system/bin/crashmonitor
#    class late_start
#    user system
#    group system log radio

# LogConfig service
service logconfig /system/bin/logconfig
    class main
    socket logconfig stream 0660 root system
    disabled
    oneshot
root@Z00A_1:/ #
This runaway modemcrash log bug was introduced by an OTA firmware update, became fairly famous, and was eventually fixed by another OTA update (I forgot the date) with a description of something like "storage optimization".

As a temporary measure, I finally made the directory read-only, so I wouldn't have to keep deleting the files; I reversed this at some point before applying the OTA update that fixed it.