Increasing layer size depending on user/group IDs

[oszi]

Description of Problem:

Edit: Not a docker issue.

How reproducible: 100%

Steps to Reproduce:

Build the following Dockerfile:

FROM debian
RUN useradd -md /data --key=UID_MIN=1000 --key=GID_MIN=1000 user

It doesn't seem to matter what base image we use.

Actual Results:

The RUN command results in a 335.1 kB layer. With a UID/GID of 10000 it results in a 3.25 MB layer;
with 30000 it's 9.73 MB; with 60000 it's 19.45 MB.

Expected Results:

I have no idea what's going on... But I'm sure the layer size shouldn't increase like this. 😨

[nalind]

Some (all?) of this appears to be useradd making sure that there's room for the user's entry in /var/log/lastlog and /var/log/faillog. If you use the -l flag when running useradd, does that prevent what you're seeing?

[oszi]

It does, thanks. That's a weird way to handle auth logs.

Closing because it's not an issue in docker.

[drewdogg]

I ran into this same problem but had the docker build fail due to running out of disk space:

$ docker build .
Sending build context to Docker daemon 2.048 kB
Sending build context to Docker daemon
Step 0 : FROM centos:7
 ---> ce20c473cd8a
Step 1 : RUN groupadd -g 213000086 cmnapp
 ---> Running in 8b29d0a916b0
 ---> cf47ae0e6ab3
Removing intermediate container 8b29d0a916b0
Step 2 : RUN useradd -u 213000086 -g cmnapp cmnapp
 ---> Running in 82b41bc5833a
ApplyLayer exit status 1 stdout:  stderr: write /var/log/lastlog: no space left on device
$ 

It now makes sense since I'm using such a big UID. Added '-l' and now it works!

[drewdogg]

Dup of #5419