Permenantly setting permissions for /dev/ttyUSB*
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Permenantly setting permissions for /dev/ttyUSB*
I wish to give ordinary users read/write access to /dev/ttyUSB* (so till software at a shop can control the till roll printer and open the till drawer).
It seems every release of CentOs changes how this should be done!
In CentOs 5, I edited /etc/udev/rules.d/50-udev.rules. I understand in CentOs 6 the rules are now in /lib/udev/rules.d, but I can't find any reference to ttyUSB in that folder, other than:
60-persistent-serial.rules(5): KERNEL!="ttyUSB[0-9]*|ttyACM[0-9]*", GOTO="persistent_serial_end"
Where should I add a rule to do the equivalent of the CentOs 5 line:
/etc/udev/rules.d/50-udev.rules:KERNEL=="ttyUSB*", GROUP="epos", MODE="0666"
(and what shoulld the rule say)
It seems every release of CentOs changes how this should be done!
In CentOs 5, I edited /etc/udev/rules.d/50-udev.rules. I understand in CentOs 6 the rules are now in /lib/udev/rules.d, but I can't find any reference to ttyUSB in that folder, other than:
60-persistent-serial.rules(5): KERNEL!="ttyUSB[0-9]*|ttyACM[0-9]*", GOTO="persistent_serial_end"
Where should I add a rule to do the equivalent of the CentOs 5 line:
/etc/udev/rules.d/50-udev.rules:KERNEL=="ttyUSB*", GROUP="epos", MODE="0666"
(and what shoulld the rule say)
Re: Permenantly setting permissions for /dev/ttyUSB*
What does `ls -la /dev/ttyUSB*` say with the standard udev rules in place?
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Re: Permenantly setting permissions for /dev/ttyUSB*
This was more of an exploratory question - I am testing and debugging my install scripts on a VM, and I don't think I can attach the actual USB hardware to the VM (I don't have drivers for the host O/S).
However, I am burning a real CentOs 6 DVD as we speak, preparatory to installing it on a real box, so I'll let you know.
In the mean time, a pointer to documentation on how the CentOs 6 rules work would be nice?
However, I am burning a real CentOs 6 DVD as we speak, preparatory to installing it on a real box, so I'll let you know.
In the mean time, a pointer to documentation on how the CentOs 6 rules work would be nice?
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Re: Permenantly setting permissions for /dev/ttyUSB*
Turns out I won't be able to answer your question for a while - CentOs 6 won't install on the old target hardware I have to hand (no pae or cx8, so I have to wait for the client to decide on and procure the new target hardware before I can actually check out the printer hardware.
So an answer based on theory, rather than practice, would be nice!
So an answer based on theory, rather than practice, would be nice!
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Re: Permenantly setting permissions for /dev/ttyUSB*
[quote]
nikkilocke wrote:
This was more of an exploratory question - I am testing and debugging my install scripts on a VM, and I don't think I can attach the actual USB hardware to the VM (I don't have drivers for the host O/S).[/quote]
Perhaps not relevant to CentOS, but it is a rare host OS that does not have native USB drivers. Many virtualization methods allow USB passthrough.
[quote]
In the mean time, a pointer to documentation on how the CentOs 6 rules work would be nice?[/quote]
How about some help from a google on [url=http://www.google.com/search?q=%22%2Fetc%2Fudev%2Frules.d%2F%22+%22%2Flib%2Fudev%2Frules.d%2F%22+site%3Aredhat.com&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a]"/etc/udev/rules.d/" "/lib/udev/rules.d/" site:redhat.com[/url]?
First, according to [url=https://bugzilla.redhat.com/show_bug.cgi?id=464844#c3]upstream[/url]:
"/lib/udev/rules.d is for operating system provided rules that shouldn't be edited. /etc/udev/rules.d is for system-specific configuration"
For details see the [url=http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/udev_device_manager.html]upstream docs.[/url]
nikkilocke wrote:
This was more of an exploratory question - I am testing and debugging my install scripts on a VM, and I don't think I can attach the actual USB hardware to the VM (I don't have drivers for the host O/S).[/quote]
Perhaps not relevant to CentOS, but it is a rare host OS that does not have native USB drivers. Many virtualization methods allow USB passthrough.
[quote]
In the mean time, a pointer to documentation on how the CentOs 6 rules work would be nice?[/quote]
How about some help from a google on [url=http://www.google.com/search?q=%22%2Fetc%2Fudev%2Frules.d%2F%22+%22%2Flib%2Fudev%2Frules.d%2F%22+site%3Aredhat.com&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a]"/etc/udev/rules.d/" "/lib/udev/rules.d/" site:redhat.com[/url]?
First, according to [url=https://bugzilla.redhat.com/show_bug.cgi?id=464844#c3]upstream[/url]:
"/lib/udev/rules.d is for operating system provided rules that shouldn't be edited. /etc/udev/rules.d is for system-specific configuration"
For details see the [url=http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Logical_Volume_Manager_Administration/udev_device_manager.html]upstream docs.[/url]
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Re: Permenantly setting permissions for /dev/ttyUSB*
Thanks for the pointer to the upstream docs. Is there no corresponding doc website for CentOs? (It might work a bit better - the search results page in the RedHat one is a total mess when viewed with Chrome.)
I have read that page, and the adjoining ones (which seem to be about Logical Volumne Management, which, AFAIK, is something to do with disks. I have copied the sample rules file from .usr/share/docs/device-mapper* into /lib/udev/rules.d
I am still totally baffled as to how to write a rule which will match /dev/ttyUSB*, and set the ownership and permissions.
What is a "DM device"?
Do I put in a rule like:
KERNEL=="ttyUSB*", GROUP="epos", MODE="0666"
or do the rules in this file have to begin with "ENV{DM"
Are the rules executed in filename alphanumeric order? If so, what happens if 2 rules match the same device?
Will the rule at the start of this file
ENV{DM_UDEV_RULES_VSN}!="?*", GOTO="dm_end"
cause any rules I add later to be skipped?
Am I even using the right file?
Am I alone in wanting to read some documentation which tells me what to do, instead of fiddling about to find out what works?
Sorry, I'm getting carried away now :-)
I have read that page, and the adjoining ones (which seem to be about Logical Volumne Management, which, AFAIK, is something to do with disks. I have copied the sample rules file from .usr/share/docs/device-mapper* into /lib/udev/rules.d
I am still totally baffled as to how to write a rule which will match /dev/ttyUSB*, and set the ownership and permissions.
What is a "DM device"?
Do I put in a rule like:
KERNEL=="ttyUSB*", GROUP="epos", MODE="0666"
or do the rules in this file have to begin with "ENV{DM"
Are the rules executed in filename alphanumeric order? If so, what happens if 2 rules match the same device?
Will the rule at the start of this file
ENV{DM_UDEV_RULES_VSN}!="?*", GOTO="dm_end"
cause any rules I add later to be skipped?
Am I even using the right file?
Am I alone in wanting to read some documentation which tells me what to do, instead of fiddling about to find out what works?
Sorry, I'm getting carried away now :-)
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Re: Permenantly setting permissions for /dev/ttyUSB*
CentOS has yet to get their act together with hosting the EL6 documentation. Sorry I can't answer your questions without research, and no time now.
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Re: Permenantly setting permissions for /dev/ttyUSB*
Thanks for the help you have given, I appreciate it.
I guess I will wait until I have the target hardware, and fiddle about until I get something that works.
I hate that, but I suppose I'm using a free operating system, and shouldn't complain!
I guess I will wait until I have the target hardware, and fiddle about until I get something that works.
I hate that, but I suppose I'm using a free operating system, and shouldn't complain!
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Permenantly setting permissions for /dev/ttyUSB*
You still have not answered the question in post #2.
You might need to add your users to the terminal's group.
You might need to add your users to the terminal's group.
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Re: Permenantly setting permissions for /dev/ttyUSB*
Do you mean the question asked by TrevorH?
If so, I answered as best I could in posts #3 and #4 - I am not in a position to run the command you suggest, because I am unable to install CentOs on the hardware I have here, and I am unable to attach the relevant device to the VM I am testing in.
I will have to wait until I have CentOs installed on hardware to which I can attach the printer before I can proceed further.
If so, I answered as best I could in posts #3 and #4 - I am not in a position to run the command you suggest, because I am unable to install CentOs on the hardware I have here, and I am unable to attach the relevant device to the VM I am testing in.
I will have to wait until I have CentOs installed on hardware to which I can attach the printer before I can proceed further.