Question: Today I update the ArchLinux use `pacman -Syu`, but it reported some error. I didn't pay attention. Then I rebooted the machine and now it reports a kernel panic.

[I found the news](https://www.archlinux.org/news/update-filesystem-201301-1-and-glibc-217-2-together/)

But it didn't tell that the kernel could panic. I cannot even login to the system.

Answer: 
1. Boot the live media
2. Mount root partition to `/mnt`
3. check `/mnt/var/log/pacman.log`
4. Handle all `.pacnews`'s listed (should find most/all in `/etc/` or in your case `/mnt/etc/`)
5. Make sure your `mkinitcpio.conf` has the latest hooks in it.
6. Check `archlinux.org`'s or subscribe to the mailing lists for update instructions if manual intervention is needed.
7. **UPDATE MORE OFTEN**

Without any logs or anymore information that's about as much information and/or help as we'll be able to give you. ***Arch Linux is a rolling release*** and a distribution that requires the user to think more than most. If you can not update it often (I run pacman -Syu everyday) then you should consider running another distribution.
1. Boot into a Live USB/CD.
2. Mount your Arch partition to `/mnt`.
3. If you have a newer Live USB/CD, chroot into it using `arch-chroot /mnt`. If not, follow the instructions in the [Change Root article](https://wiki.archlinux.org/index.php/Change_Root).
4. Run `sudo pacman -Syu` and *carefully* note what goes wrong (if anything). You might have to run `dhcpcd` to get your internet connection to work.
5. Exit out, unmount your partitions, etc. and it should work.