On 08/05/2021 15.34, -pj wrote:
On 5/8/21 6:33 AM, Carlos E. R. wrote:
> On 08/05/2021 08.43, -pj wrote:
And you can see that user "cer" has "rw" permissions.
Great explanation on this. I can see this now and understand the link
from: /dev/cdrom ->sr0 -to- /dev/sr0 -to- getfacl /dev/sr0
ACLS is something new to me most certainly. Noting the "+" in the
permissions of the actual device makes alot more sense seeing the
"getfacl" commands output. I see there is a man page for the getfacl
command also. This answers my question as to why the K3b application
worked..well with displaying the error listed above. The actual device
is /dev/sr0 and user:username:rw- does have read and write permissions.
Basically the entire output of getfacl /dev/sr0 comes together with
#group: cdrom since /dev/cdrom -> has rwxrwxrwx permissions (any user
Huh, the last line is not correct. cdrom is a symplink, its permissions
are ignored. Instead, the permissions of what is pointed by the link apply.
The rest, perfect.
Ah, getfacl has a companion setfacl.
1. Can I ask about the following possibly?: Prefixes in the /dev
directory have l,c and b (which is the prefix for /dev/sr0). Is there a
fairly quick explanation for these by chance.
b block device
c char device
There was a text file in "/usr/src/linux/Documentation" (if the kernel
sources are installed) that described every possible device file in
/dev. I can not find it now. Ah! Found it:
The other important data in /dev is the Major-Minor numbers.
cer@Telcontar:~> l /dev/sr0
brw-rw----+ 1 root cdrom 11, 0 May 4 19:49 /dev/sr0
sr0 is block, major 11, minor 0. So, looking at the file I mentioned, then:
11 char Raw keyboard device (Linux/SPARC only)
0 = /dev/kbd Raw keyboard device
11 char Serial Mux device (Linux/PA-RISC only)
0 = /dev/ttyB0 First mux port
1 = /dev/ttyB1 Second mux port
11 block SCSI CD-ROM devices
0 = /dev/scd0 First SCSI CD-ROM
1 = /dev/scd1 Second SCSI CD-ROM
The prefix /dev/sr (instead of /dev/scd) has been
Well, it should be "/dev/scd0", which apparently will be the new name
Originally, the major-minor number were one byte each. It is those three
"infos" which tells what "driver" associates with each device file.
The excellent answers to my question here has really
helped me to
understand more that a software message does not necessarily mean that
it knows exactly what it is trying to convey. I really appreciate the
2. I notice that /dev/cdrw -> sr0 is not listed in getfacl /dev/sr0
It is a symlink, so you only have to look at the permissions of sr0.
How is it
done? Well, the "display manager" does that job when you login.
"In simple terms, a display manager is a program that provides
graphical login capabilities for your Linux distribution. It controls
the user sessions and manages user authentication. Display manager
starts the display server and loads the desktop environment right
after you enter your username and password.Dec 4, 2020"
gdm, wdm, kdm, sddm...
Thanks for adding this portion on display managers also.
technique is used to grant you permissions to use devices
connected on the USB.
I think that "polkit" is also part of the system, but that's an area
that I know little about. See "man polkit" perhaps.
I feel more comfortable now able to look over the warning displayed in
K3b. The tip on polkit is interesting also.
Cheers / Saludos,
Carlos E. R.
(from 15.2 x86_64 at Telcontar)