Trouble shooting

Checking file checksums

There's a lot of shoddy media out there. If you experience unexpected exceptions, crashes, or anything unusual, it's generally a good idea to verify that your files were copied to your SD card properly in the first place. Some things I do:

1. properly unmount USB drives, always. example: umount /media/nick/6332-3234
2. unplug/replug device
3. check checksums, example: sha1sum arch/arm/boot/zImage /media/nick/6332-3234/linux/zImage

• if these don't match, re-copy file and goto 1, otherwise:

4. repeat 1

If your fat32 drive starts acting up, you might see some warnings in dmesg like:

[42862.686450] print_req_error: I/O error, dev sda, sector 20776
...
[42862.686455] Buffer I/O error on dev sda1, logical block 12584, lost async page write
...
[42863.138365] FAT-fs (sda1): unable to read boot sector to mark fs as dirty

you generally just need to fsck your disk, example: sudo fsck.msdos -aw /dev/sda1, though be careful to check that /dev/sd1 is your SD card.