Using the CSE/CC Linux Mirror

Debian-based Distros

Boomer-friendly
Stable
Use apt for managing packages

APT and Mirrors

APT downloads from the package archive (archive.ubuntu.com, deb.debian.org)
Or a “mirror” of the repository (in.archive.ubuntu.com)

prsingh@turing:~$ apt moo
                 (__) 
                 (oo) 
           /------\/ 
          / |    ||   
         *  /\---/\ 
            ~~   ~~   
..."Have you mooed today?"...

The CC has a mirror: ftp.cc.iitk.ac.in/mirror. Visible on LAN.
CSE has a mirror: mirror.cse.iitk.ac.in. Visible on the internet.
These mirrors offer 8-30 MBps on the LAN, up to 70 on wired connections. (The public mirrors offer 1-10.)
iitk wifi beats iitk-sec for this stuff

Configuring Mirrors

Configured apt mirrors are listed in /etc/apt/sources.list (old) or /etc/apt/sources.list.d/ubuntu.sources (new).
Side note - You can have multiple mirrors for out-of-repository software like ROS/Chrome (Not recommended.)
Side note - You can download debs from the mirrors under /pool and manually dpkg --install them. I did that from Ubuntu when I couldn’t find gdb-doc under Debian. (Not recommended.)
man sources.list.5

Old Sources File

At /etc/apt/sources.list

# deb cdrom:[Debian GNU/Linux 12.0.0 _Bookworm_ - Official amd64 NETINST with firmware 20230610-10:21]/ bookworm main non-free-firmware

# I used bookworm (Debian 12) earlier.
# deb http://mirror.cse.iitk.ac.in/debian bookworm main non-free-firmware non-free
# deb-src http://mirror.cse.iitk.ac.in/debian bookworm main non-free-firmware non-free

deb http://mirror.cse.iitk.ac.in/debian trixie main non-free-firmware non-free
deb-src http://mirror.cse.iitk.ac.in/debian trixie main non-free-firmware non-free
# EOF

New Sources File

At /etc/apt/sources.list.d/ubuntu.sources

Types: deb
URIs: http://ftp.cc.iitk.ac.in/mirror/ubuntu
Suites: noble noble-updates noble-backports
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg

Types: deb
URIs: http://ftp.cc.iitk.ac.in/mirror/ubuntu
Suites: noble-security
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg
# EOF

Another example:

# Modernized from /etc/apt/sources.list
Types: deb deb-src
# URIs: http://mirror.cse.iitk.ac.in/debian/
URIs: http://deb.debian.org/debian
Suites: trixie
Components: main non-free-firmware
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg


Types: deb deb-src
# URIs: http://mirror.cse.iitk.ac.in/debian-security
URIs: http://deb.debian.org/debian-security
Suites: trixie-security
Components: main non-free-firmware
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg
# EOF

What You Need to Do

Replace deb.debian.org or http://archive.ubuntu.com/ubuntu/ with the CC/CSE mirror
Warning 1 - the CC mirror isn’t accessible on campus. You’ll miss out on security updates at home. Uncomment it when you’re out.
Warning 2 - both CC/CSE mirrors have had some issue with Debian for a month.
Warning 3 - CSE’s Ubuntu mirror is sometimes outdated.
Checking if a mirror is outdated - apt update-ing on the local and root mirrors should show the same output.

When Installing Ubuntu/Debian

Lot of apt downloads, updates. Because your ISO image is probably old.
Try using one of these mirrors.
The Ubuntu installer doesn’t let you choose.
Until recently (or in my old ISO image), the Debian installer lets you choose CSE’s mirror because it is visible outside as well.
If installing for a project Virtual Machine, do not connect to the internet. You can do without those security updates.

What Those Lines Mean

deb is precompiled, compressed binaries (with manuals, copyrights, etc).
deb-src is source code. (apt source gcc downloads the actual source.)
Suite - One version of one OS. Noble is Ubuntu 24, Bookwork is Debian 12, etc.
Components: you can choose to exclude closed source software

Example - A Modified Ubuntu Sources File

Note the prompt - it has the file location.

dhruv@dhruv-Inspiron:/$ cat /etc/apt/sources.list.d/ubuntu.sources
# default
# Types: deb
# URIs: http://archive.ubuntu.com/ubuntu/
# Suites: noble noble-updates noble-backports
# Components: main restricted universe multiverse
# Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg
# 
# Types: deb
# URIs: http://security.ubuntu.com/ubuntu/
# Suites: noble-security
# Components: main restricted universe multiverse
# Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg


# WARNING - will not work outside intranet.
# ghar ja ke change karna
Types: deb
URIs: http://ftp.cc.iitk.ac.in/mirror/ubuntu
Suites: noble noble-updates noble-backports
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg

Types: deb
URIs: http://ftp.cc.iitk.ac.in/mirror/ubuntu
Suites: noble-security
Components: main restricted universe multiverse
Signed-By: /usr/share/keyrings/ubuntu-archive-keyring.gpg

# EOF

Acknowledgments

Dhruva, a friend from school, told me about IITK’s mirrors.
Didn’t get help/pointers from people in the esteemed department.
Used pandoc to convert markdown (my favourite) to HTML.