Gentoo Forums
Gentoo Forums
Gentoo Forums
Quick Search: in
source of /tmp/{portage,screen} directories? [in progress]
View unanswered posts
View posts from last 24 hours

 
Reply to topic    Gentoo Forums Forum Index Other Things Gentoo
View previous topic :: View next topic  
Author Message
CaptainBlood
Advocate
Advocate


Joined: 24 Jan 2010
Posts: 3977

PostPosted: Tue Aug 20, 2024 12:12 pm    Post subject: source of /tmp/{portage,screen} directories? [in progress] Reply with quote

openrc here:
Code:
rc-update
            alsasound | boot                                   
               binfmt | boot                                   
             bootmisc | boot                                   
              cgroups |                                 sysinit
               cronie |      default                           
                devfs |                                 sysinit
               dhcpcd |      default                           
      display-manager |      default                           
                dmesg |                                 sysinit
              elogind | boot                                   
                 fsck | boot                                   
             hostname | boot                                   
              hwclock | boot                                   
              keymaps | boot                                   
            killprocs |                        shutdown       
    kmod-static-nodes |                                 sysinit
                local |      default nonetwork                 
           localmount | boot                                   
             loopback | boot                                   
              modules | boot                                   
             mount-ro |                        shutdown       
                 mtab | boot                                   
     opentmpfiles-dev |                                 sysinit
   opentmpfiles-setup | boot                                   
               procfs | boot                                   
                 root | boot                                   
         save-keymaps | boot                                   
    save-termencoding | boot                                   
            savecache |                        shutdown       
                 sshd |      default                           
                 swap | boot                                   
               sysctl | boot                                   
                sysfs |                                 sysinit

Code:
drwxrwxr-x 2 portage portage 4096 août  20 14:32 portage
drwxrwxr-x 2 root    utmp    4096 août  20 14:32 screen
srwxrwxrwx 1 user    user       0 août  20 14:33 dbus-8L6Wzo9PJ5

portage seems obvious,
dbus seems X11 related.

Wondering which process creates that directory?

Thks 4 ur attention, interest & support.
_________________
USE="-* ..." in /etc/portage/make.conf here, i.e. a countermeasure to portage implicit braces, belt & diaper paradigm
LT: "I've been doing a passable imitation of the Fontana di Trevi, except my medium is mucus. Sooo much mucus. "


Last edited by CaptainBlood on Wed Aug 21, 2024 5:48 pm; edited 2 times in total
Back to top
View user's profile Send private message
Goverp
Advocate
Advocate


Joined: 07 Mar 2007
Posts: 2186

PostPosted: Tue Aug 20, 2024 12:20 pm    Post subject: Reply with quote

In my case, yours may differ, it's the result of running "screen" on a tty to get scrollback.
_________________
Greybeard
Back to top
View user's profile Send private message
CaptainBlood
Advocate
Advocate


Joined: 24 Jan 2010
Posts: 3977

PostPosted: Tue Aug 20, 2024 7:25 pm    Post subject: Reply with quote

Indeed, when rebooting after app-misc/screen package removal, this directory isn't created anymore...
Now the new question is how is it created?
I don't recall have set something in this regard....

As coming back to OP, the same question for /tmp/portage...
How is it created?

I may be the cause of all of this, albeit not remembering some details.
However I don't like the feeling something is happening in my back.

I really would like to know how this all happens...

Thks 4 ur attention, interest & support.
_________________
USE="-* ..." in /etc/portage/make.conf here, i.e. a countermeasure to portage implicit braces, belt & diaper paradigm
LT: "I've been doing a passable imitation of the Fontana di Trevi, except my medium is mucus. Sooo much mucus. "
Back to top
View user's profile Send private message
gentoo_ram
Guru
Guru


Joined: 25 Oct 2007
Posts: 502
Location: San Diego, California USA

PostPosted: Tue Aug 20, 2024 8:11 pm    Post subject: Reply with quote

The /tmp/screen directory is created when someone or something runs the 'screen' command. If you don't clear your /tmp directory at boot (and my set up does not) then what it means is that something ran the 'screen' command at some point.
Back to top
View user's profile Send private message
pingtoo
Veteran
Veteran


Joined: 10 Sep 2021
Posts: 1339
Location: Richmond Hill, Canada

PostPosted: Tue Aug 20, 2024 8:27 pm    Post subject: Reply with quote

CaptainBlood wrote:
However I don't like the feeling something is happening in my back.

I really would like to know how this all happens...


No one can tell what happen since everybody have different setup.

The sure way is let your computer tell you what happen. enable audit will have record what happen.

if you want to disable unknown execution, then enable selinux/apparmor/seccomp.

Don't think of above as security/hardening. You can think of it as your computer service you (the master)
Back to top
View user's profile Send private message
flexibeast
Guru
Guru


Joined: 04 Apr 2022
Posts: 473
Location: Naarm/Melbourne, Australia

PostPosted: Wed Aug 21, 2024 1:42 am    Post subject: Reply with quote

`tmp` directories are for temporary files that programs create, for various reasons, in order to do their job. It's a standard programming technique (e.g. in the blogging software i've written for my own use).

For example, when creating a file with certain contents at the user's request, a program might create a temporary file for output, only renaming that temporary file to the intended file name if the output operation was entirely successful. This avoids creating a file that doesn't contain all the intended content, which might be an issue if other programs are assuming that such a file will necessarily contain such content.

There are programs to help you determine which programs are working with certain directories and files, such as fuser(1) and lsof(8).

In the case of screen(1) in particular, the README file talks about the use of `/tmp/screen-exchange` for writing and reading the copy buffer, and the INSTALL file mentions that the `/tmp` directory can be used to create sockets when multiple users are using screen. But i can't immediately see any reference to `/tmp/screen` in the source (which might simply because that path is created on the fly, rather than being a literal).

If the creation of temporary files is a general concern for you, you should certainly become familiar with something like fuser(1), and with grep'ing the source code of the relevant program to learn why a given temporary file is being created, and for what purpose.
Back to top
View user's profile Send private message
gentoo_ram
Guru
Guru


Joined: 25 Oct 2007
Posts: 502
Location: San Diego, California USA

PostPosted: Wed Aug 21, 2024 5:07 am    Post subject: Reply with quote

The /tmp/screen string is definitely in the executable:
Code:
gw ~ # strings /usr/bin/screen-4.9.1 | grep tmp
/tmp/screen-exchange
/tmp/screen
Utmp slot not found -> not removed
What? Cannot remove Utmp slot?
/var/run/utmp
/var/run/utmp
Back to top
View user's profile Send private message
flexibeast
Guru
Guru


Joined: 04 Apr 2022
Posts: 473
Location: Naarm/Melbourne, Australia

PostPosted: Wed Aug 21, 2024 7:10 am    Post subject: Reply with quote

gentoo_ram wrote:
The /tmp/screen string is definitely in the executable

So it is - thanks for reminding me about the existence of strings(1), i keep forgetting about it for some reason ...

i actually hadn't read the original post closely enough, but doing so now brought my attention to the fact that the created "screen" directory is owned by group 'utmp', which suggests it's being used to provide support utmp(5) functionality:
Quote:
The utmp file allows one to discover information about who is currently using the system. There may be more users currently using the system, because not all programs use utmp logging.

screen's utmp stuff can be found in utmp.c. i'm in the middle of other stuff, so i've not examined that file in detail.

As an aside, the creator of s6 has written a piece of software called utmps, and on its home page, says:
Quote:
utmps is an implementation of the utmpx.h family of functions performing user accounting on Unix systems.

Traditionally, utmp functionality is provided by the system's libc. However, not all libcs implement utmp: for instance the musl libc, on Linux, does not. The main reason for it is that utmp functionality is difficult to implement in a secure way; in particular, it is impossible to implement without either running a daemon or allowing arbitrary programs to tamper with user accounting.
Back to top
View user's profile Send private message
pa4wdh
l33t
l33t


Joined: 16 Dec 2005
Posts: 892

PostPosted: Wed Aug 21, 2024 8:36 am    Post subject: Reply with quote

On my system the /tmp/screen directory is created by a tmpfiles.d entry added by the app-misc/screen package:

Code:
$ equery f screen
 * Searching for screen ...
 * Contents of app-misc/screen-4.9.1-r1:
(...)
/usr/lib/tmpfiles.d
/usr/lib/tmpfiles.d/screen.conf
(...)
$ cat /usr/lib/tmpfiles.d/screen.conf
d /tmp/screen 0775 root utmp

I guess something similar is happening on you system.
Welcome to the wonderful world of tmpfiles :(
_________________
The gentoo way of bringing peace to the world:
USE="-war" emerge --newuse @world

My shared code repository: https://code.pa4wdh.nl.eu.org
Music, Free as in Freedom: https://www.jamendo.com
Back to top
View user's profile Send private message
Goverp
Advocate
Advocate


Joined: 07 Mar 2007
Posts: 2186

PostPosted: Wed Aug 21, 2024 8:47 am    Post subject: Reply with quote

From the screen ebuild - verbatim:
Code:
ewarn "This revision changes the screen socket location to ${EROOT}/tmp/${PN}"

_________________
Greybeard
Back to top
View user's profile Send private message
CaptainBlood
Advocate
Advocate


Joined: 24 Jan 2010
Posts: 3977

PostPosted: Wed Aug 21, 2024 12:46 pm    Post subject: Reply with quote

Very nice clarifications what's happening there.:D
Code:
/tmp/portage
is also a PITA here :roll:, likely with similar origin...

Thks 4 ur attention, interest & support.
_________________
USE="-* ..." in /etc/portage/make.conf here, i.e. a countermeasure to portage implicit braces, belt & diaper paradigm
LT: "I've been doing a passable imitation of the Fontana di Trevi, except my medium is mucus. Sooo much mucus. "
Back to top
View user's profile Send private message
sam_
Developer
Developer


Joined: 14 Aug 2020
Posts: 2038

PostPosted: Wed Aug 21, 2024 12:50 pm    Post subject: Reply with quote

You can write your own snippet and/or use INSTALL_MASK if it bothers you.

For Portage, it exists for a good reason (because of privilege escalation issues).
Back to top
View user's profile Send private message
CaptainBlood
Advocate
Advocate


Joined: 24 Jan 2010
Posts: 3977

PostPosted: Wed Aug 21, 2024 1:10 pm    Post subject: Reply with quote

sam_ wrote:
For Portage, it exists for a good reason (because of privilege escalation issues).
Does letting things as they are has any implication regarding /etc/portage/make.conf content?

Thks 4 ur attention, interest & support.
_________________
USE="-* ..." in /etc/portage/make.conf here, i.e. a countermeasure to portage implicit braces, belt & diaper paradigm
LT: "I've been doing a passable imitation of the Fontana di Trevi, except my medium is mucus. Sooo much mucus. "
Back to top
View user's profile Send private message
CaptainBlood
Advocate
Advocate


Joined: 24 Jan 2010
Posts: 3977

PostPosted: Wed Aug 21, 2024 2:35 pm    Post subject: Reply with quote

CaptainBlood wrote:
sam_ wrote:
For Portage, it exists for a good reason (because of privilege escalation issues).
Does letting things as they are has any implication regarding /etc/portage/make.conf content expectation?

Thks 4 ur attention, interest & support.

_________________
USE="-* ..." in /etc/portage/make.conf here, i.e. a countermeasure to portage implicit braces, belt & diaper paradigm
LT: "I've been doing a passable imitation of the Fontana di Trevi, except my medium is mucus. Sooo much mucus. "
Back to top
View user's profile Send private message
Zucca
Moderator
Moderator


Joined: 14 Jun 2007
Posts: 3776
Location: Rasi, Finland

PostPosted: Wed Aug 21, 2024 3:06 pm    Post subject: Reply with quote

CaptainBlood wrote:
sam_ wrote:
For Portage, it exists for a good reason (because of privilege escalation issues).
Does letting things as they are has any implication regarding /etc/portage/make.conf content?

Thks 4 ur attention, interest & support.
If you change the default temp directories of portage in make.conf, then you should edit appropriate tmpfiles.d -file too. See inside /usr/lib/tmpfiles.d/portage-tmpdir.conf. If you want to make changes there you should copy that file into /etc/tmpfiles.d/ and then edit it.
_________________
..: Zucca :..

My gentoo installs:
init=/sbin/openrc-init
-systemd -logind -elogind seatd

Quote:
I am NaN! I am a man!
Back to top
View user's profile Send private message
CaptainBlood
Advocate
Advocate


Joined: 24 Jan 2010
Posts: 3977

PostPosted: Wed Aug 21, 2024 5:19 pm    Post subject: Reply with quote

Here is:
Code:
grep /var/tmp /etc/fstab
tmpfs               /var/tmp           tmpfs      rw,nosuid,noatime,nodev,,mode=1777                                   0 0
tmpfs               /var/tmp/portage   tmpfs      rw,nosuid,noatime,nodev,,uid=portage,gid=portage,x-mount.mkdir=775   0 0
Code:
grep /var/tmp /etc/portage/make.conf
PORTAGE_TMPDIR="/var/tmp"
Zucca wrote:
See inside /usr/lib/tmpfiles.d/portage-tmpdir.conf. If you want to make changes there you should copy that file into /etc/tmpfiles.d/ and then edit it.
Code:
cat /usr/lib/tmpfiles.d/portage-tmpdir.conf
d /var/tmp/portage 0775 portage portage
d /tmp/portage 0775 portage portage
Why is there TWO such items, where ONE sounds reasonable enough?

Maybe to help
sam_ wrote:
privilege escalation issues.
?

Sorry to say but that sounds a little confusing of an implementation...

Thks 4 ur attention, interest & support.
_________________
USE="-* ..." in /etc/portage/make.conf here, i.e. a countermeasure to portage implicit braces, belt & diaper paradigm
LT: "I've been doing a passable imitation of the Fontana di Trevi, except my medium is mucus. Sooo much mucus. "
Back to top
View user's profile Send private message
CaptainBlood
Advocate
Advocate


Joined: 24 Jan 2010
Posts: 3977

PostPosted: Wed Aug 21, 2024 5:51 pm    Post subject: Reply with quote

Goverp wrote:
In my case, yours may differ, it's the result of running "screen" on a tty to get scrollback.
Interesting.
Any detail how you proceed if not manually?

Thks 4 ur attention, interest & support.
_________________
USE="-* ..." in /etc/portage/make.conf here, i.e. a countermeasure to portage implicit braces, belt & diaper paradigm
LT: "I've been doing a passable imitation of the Fontana di Trevi, except my medium is mucus. Sooo much mucus. "
Back to top
View user's profile Send private message
Zucca
Moderator
Moderator


Joined: 14 Jun 2007
Posts: 3776
Location: Rasi, Finland

PostPosted: Wed Aug 21, 2024 7:33 pm    Post subject: Reply with quote

CaptainBlood wrote:
Code:
cat /usr/lib/tmpfiles.d/portage-tmpdir.conf
d /var/tmp/portage 0775 portage portage
d /tmp/portage 0775 portage portage
Why is there TWO such items, where ONE sounds reasonable enough?
I read somewhere that those to locations were chosen because those are the two most common locations for portage temporary directory.
IMO Portage should simply handle the temporary direction creation and permission internally.
Or via /var/lib/tmpfiles.d... if that was supported.
_________________
..: Zucca :..

My gentoo installs:
init=/sbin/openrc-init
-systemd -logind -elogind seatd

Quote:
I am NaN! I am a man!
Back to top
View user's profile Send private message
Goverp
Advocate
Advocate


Joined: 07 Mar 2007
Posts: 2186

PostPosted: Thu Aug 22, 2024 9:49 am    Post subject: Reply with quote

CaptainBlood wrote:
Goverp wrote:
In my case, yours may differ, it's the result of running "screen" on a tty to get scrollback.
Interesting.
Any detail how you proceed if not manually?

Not sure what your question is, so I'll answer some I might have asked:

To be general, sometimes when I switch to a tty to run say emerge --update (which I prefer not to do from KDE konsole), and I know there will be lots of output that I want to scroll through, I run "screen". I don't use all its features - the only key combination I know is Ctl+A+[ - to initiate scrollback! I run it manually - normally my tty sessions are just for a quick check on something that needs root (my everyday userid is not in wheel).

My /tmp is recreated on boot - I very vaguely recall some option I set when I first installed Gentoo, but that was so long ago, I forget what - so /var/tmp disappears unless I start screen again.
_________________
Greybeard
Back to top
View user's profile Send private message
Display posts from previous:   
Reply to topic    Gentoo Forums Forum Index Other Things Gentoo All times are GMT
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum