Linux Servers is a free eBook by Paul Cobbaut that talks about Linux servers in depth. Cobbaut covers various topics like apache web server, squid, sql, DNS, advanced DNS, DHCP, Routers, Firewall, Samba, File Servers, SELinux, GIT, IPV6 etc. in depth. Spanning over 239 pages, this book should help you address most of the common problems that newbies face while learning how the Linux Servers work.
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