What is the function of bootstrap.log?

Question

I encountered the existence of a file named bootstrap.log in the /var/log directory when trying to solve a log related problem and when looking at its content I saw that the timestamps are over a year old.

It seems to be consisting of a lot FTP-links, dpkg-warnings like "ignoring pre-dependency problem!" and information concerning unpacking .deb-packages, which seems to be pointing to installation related data.

To see if a relation existed with the installation date I did:

$ ls -lt /var/log/installer
total 752
-rw-r--r-- 1 root root 387038 dec 17  2022 initial-status.gz
-rw------- 1 root root 277005 dec 17  2022 syslog
-rw------- 1 root root   1509 dec 17  2022 casper.log
-rw-r--r-- 1 root root     64 dec 17  2022 media-info
-rw------- 1 root root  91778 dec 17  2022 debug

From which I conclude that the installation took place at dec 17, 2022.

The timestamped entries in bootstrap.log all start with 2022-08-09, so this would be before the installation.

I searched for information on bootstrap.log, but could not find enlightening information on the subject.

This made me wonder what exactly the of use bootstrap.log is, why it has been created and if its content will change at all after its original creation date.

I am on Ubuntu 20.04.3

Answer 1

That log file was created by the utility(program) used to prepare (install into a directory on some machine) your Ubuntu system before it was made into an ISO image to be downloaded and installed on user machines like yours.

It's there as a verification (trace origin) mechanism.

It's not going to change in your already installed Operating System's lifetime.

The remote links i.e. FTP, HTTP ... etc. or local ones and files are the addresses/links to resources on which the original resources(Ubuntu or Debian systems) were kept.

This process is in layman's terms, a process during which an original system gets selectively installed into a separate directory while selecting(or even creating/adding) or excluding certain parts(packages, hierarchy, files and links) of that system to create a certain target "flavor" for a certain architecture based on a pre-configured set of instructions.

Two famous tools used for that process are debootstrap and cdebootstrap ... /var/log/bootstrap.log is likely created by the latter one.

Answer 2

See the man page:

cdebootstrap builds a basic Debian system of CODENAME (e.g. jessie, stretch, sid) from ORIGIN (e.g Debian, Ubuntu) into TARGET using the source specified in MIRROR. It supports http://, ftp://, file:// and ssh:// URL and defaults to http://ftp.debian.org/debian. The ssh:// scheme uses cat on the remote host to access the files. You have to setup a master connection and configure ssh to use it or use a key for authentication. No user interaction is possible. The complete log is saved as /var/log/bootstrap.log in the new system.

...

FLAVOURS

Flavours available with default configuration:

build Installs essential, apt and build-essential. Suitable for sbuild and pbuilder usage. All rc.d operations are disabled by a policy-rc.d script (cdebootstrap- helper-rc.d package).

minimal Installs essential and apt. All rc.d operations are disabled by a policy-rc.d script (cdebootstrap-helper-rc.d package).

standard Installs required and important priority packages. This is the default flavour.