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# Shows the last 10 lines of a file 
tail /var/log/<logfile>

# Shows the first 5 Lines of a file
head -5 /var/log/<logfile>

# Live Logfile View for the last 10 Lines
tail -f /var/log/<logfile>

# Show the whole content of a file
cat /var/log/<logfile>

Possible other useful commands:

zcat – Displays all the contents of logfile.gz

zmore – See the file in pages, without decompressing the files

zgrep – Search inside a compressed file


How To View and Configure Linux Logs on Ubuntu and Centos | DigitalOcean
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