Will Senn wrote:
Hi,
I'm exploring my newly minted lfs-7.8-rc1 instance, which after many
painful crashes and troubleshooting bouts, has successfully booted with
no errors. Yeeha!
In my exploration, I am investigating how passwd is shadowed and such.
In my investigation, I came across the utility pwck, which checks the
integrity of such files and I ran it. When I did, it reported:
user 'messagebus' : directory '/var/run/dbus' does not exist
So, I looked at the password file using vipw, which showed:
messagebus:x:18:18:D-Bus Message Daemon User:/var/run/dbus:/bin/false
I didn't know what this meant exactly, so I looked at man passwd, which
told me about the command passwd but also pointed me to man 5 passwd,
which explained the passwd file format and said that it meant:
login name:encrypted password, user id, group id, user name/comment:home
directory:command interpreter
From all of this it appears that the messagebus user is supposed to
have a home directory named '/var/run/dbus' even though they don't have
a true shell to log in to. My take on this is that messagebus is a
system user (user id < 100) that has something to do with a D-Bus
Message Daemon, a daemon that facilitates inter-application
communication (googled it).
I looked around for anything that looked like a dbus in /etc/rc/init.d:
find ./ -iname "*db*"
But I didn't see anything promising. I then looked in the LFS book and
found where I held full responsibility for and had created the passwd
file, in 6.6, but no other dbus references.
In looking for info about /var/run/..., things seem a little convoluted.
It appears that my /var/run is a symlink to /run. I read a bit about
/var/run and it would appear that this is not supposed to be persistent
across boots (see 7.2.2 cleanfs), so it doesn't seem like the admin is
supposed to create anything in there (but the system populates it on boot).
I have three questions:
1. Is the messagebus user necessary for a base LFS instance or is it
there because it will quickly be needed (say, in BLFS)?
It is in LFS to make the book as compatible as possible with LFS-systemd
which installs dbus.
2. If the messagebus user is necessary, does it matter that the
/var/run/dbus folder is missing?
No.
3. If it matters, then how does the /var/run/dbus folder get created?
/var/run is a symlink to /run which is a tmpfs created at each boot.
/var/run/dbus is created by dbus when the daemon starts.
-- Bruce
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