New Perspectives On Web Design

CHAPTER 8 How to Fix The Web: Obscure Back-End Techniques and Terminal Secrets

web SeRveR eRRoR logS

If it failed to start and didn’t give a friendly error message, the next place

to look is the error logs. These are usually in the /var/log directory named

after the software. Run ls /var/log to double check. For example, Apache’s

logs are in /var/log/apache2.

$ ls -l /var/log/apache2/*log*

-rw-r----- 1 root adm 1944899 May 5 09:59 /var/log/nginx/access.log

-rw-r----- 1 root adm 538152 May 4 02:40 /var/log/nginx/access.

log.2.gz

-rw-r----- 1 root adm 28647 May 5 08:18 /var/log/nginx/error.log

-rw-r----- 1 root adm 5701 May 4 02:35 /var/log/nginx/error.log.2.gz

This shows that Apache has an access log and an error log. Both logs are

zipped up around 02:30 each morning. The next command first changes

into the /var/log/apache2 directory with the cd command, and then uses

tail to view the last few entries in a log file.

$ cd /var/log/apache2; tail error.log

To look at a gzipped log file, use the zcat command to output it and

pipe through tail. The -20 shows the last 20 lines.

$ zcat error.log.2.gz | tail -20

Or better yet, just look for errors using grep. Use zcat with the -f

option to display both normal and zipped log files. Then pipe the output

through grep to search for the word “error” case insensitively:

$ zcat -f error.log* | grep -i error

This command may produce a lot of output. If a Matrix fan happens to

walk past your computer right now, they’ll be impressed to see all that raw

data whizzing by. It won’t help you much, though, so pipe it through less:

$ zcat -f error.log* | grep -i error | less