How to show the number of subordinate UIDs for a user?

[eriksjolund]

Is there an easy way to show the number of subordinate UIDs for a user?
(I'm looking for a command-line tool)

I see there is uidmap information in the output from podman info:

$ podman info | grep -A 6 uidmap
    uidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
$ 

Is it maybe possible by using podman info --format with a clever format string?

(I haven't learned that syntax yet)

Note also:
"Multiple ranges may be specified per user."
a quote from:
https://man7.org/linux/man-pages/man5/subuid.5.html

An example of what I'm looking for

For example, this configuration

[testpodman@localhost ~]$ grep -r $USER /etc/subuid
testpodman:362144:65536
[testpodman@localhost ~]$

would yield this result

[testpodman@localhost ~]$ num_subuids $USER
65536
[testpodman@localhost ~]$

(The command num_subuids does not yet exist).

Just being able to detect the number of subordinate UIDs for the current user would also be fine.

[vrothberg]

Thanks for reaching out, @eriksjolund!

The format string you're looking for is: podman info --format "{{ (index .Host.IDMappings.UIDMap 1).Size}}"

[Luap99]

AFAIK This will panic when the user has no subordinate IDs.
This should work better and print 0 when there are no extra IDs :
podman info --format "{{if eq (len .Host.IDMappings.UIDMap) 1}}0{{else}}{{ (index .Host.IDMappings.UIDMap 1).Size}}{{end}}"

[vrothberg]

That looks even better, thanks @Luap99 !

[eriksjolund]

Thanks @vrothberg @Luap99 for the suggestions!
It works for a single range but not for multiple ranges:

[testuser@localhost ~]$ podman info | grep -A9 uidmap
    uidmap:
    - container_id: 0
      host_id: 1006
      size: 1
    - container_id: 1
      host_id: 493216
      size: 65536
    - container_id: 65537
      host_id: 593216
      size: 65536
[testuser@localhost ~]$ 

[testuser@localhost ~]$ grep testuser /etc/subuid
testuser:493216:65536
testuser:593216:65536
[testuser@localhost ~]$  podman info --format "{{if eq (len .Host.IDMappings.UIDMap) 1}}0{{else}}{{ (index .Host.IDMappings.UIDMap 1).Size}}{{end}}"
65536
[testuser@localhost ~]$ 

I would have expected to see:
131072

(65536 + 65536)

[Luap99]

You could loop over the ranges with the template but I do not think you can add them together into one integer.

[eriksjolund]

@Luap99 Good to know.

I tried out the range version and used bash to add the numbers (and subtract 1):

[testuser@localhost ~]$ grep testuser /etc/subuid
testuser:493216:65536
testuser:593216:65536
[testuser@localhost ~]$ echo $(( $(podman info --format "{{ range .Host.IDMappings.UIDMap }}+{{.Size }}{{end }}" ) - 1 ))
131072
[testuser@localhost ~]$ 

(I hope I got it right)

[Luap99]

This looks good to me.