medusa# mount | egrep '^/dev' /devices on /devices read/write/setuid/devices/rstchown/dev=9640000 on Fri Jan 19 16:33:07 2018 /dev on /dev read/write/setuid/devices/rstchown/dev=9680000 on Fri Jan 19 16:33:07 2018 /dev/fd on fd read/write/setuid/devices/rstchown/dev=9940001 on Fri Jan 19 16:33:22 2018 medusa# ls -l /dev/rdsk/c1t*d0 lrwxrwxrwx   1 root     root          65 Jan  2  2015 /dev/rdsk/c1t0d0 -> ../../devices/pci at 0,0/pci8086,340b at 4/pci1028,1f10 at 0/sd at 0,0:wd,raw lrwxrwxrwx   1 root     root          65 Jan  2  2015 /dev/rdsk/c1t1d0 -> ../../devices/pci at 0,0/pci8086,340b at 4/pci1028,1f10 at 0/sd at 1,0:wd,raw medusa# uname -a SunOS medusa 5.11 11.3 i86pc i386 i86pc On 2/6/2018 9:06 PM, Dan Cross wrote: > On Tue, Feb 6, 2018 at 8:48 PM, Dave Horsfall > wrote: > > On Wed, 7 Feb 2018, Greg 'groggy' Lehey wrote: > > V3 and earlier still *called* them special files, but it > seems they were essentially just magic inode numbers > (there was no physical file on disk, just any directory > entry with the given inode would be the special file). > > > Isn't that still the case? > > > Wasn't that "devfs" (which Penguin/OS calls "udev")?  I've never > grokked that concept. > > > No. devfs was (is?) a pseudo-filesystem where only special files > corresponding to the devices enumerated by the kernel during > autoconfiguration are present. The contents are synthesized at boot > time and the filesystem is mounted at some canonical location (like > /dev), but is otherwise ephemeral. This is in contrast to the older > /dev, which is usually just a directory on the root filesystem, > wherein one created a number of device files that may (or may not) > correspond to an actual hardware device in the system (remember the > old dance of, "cd /dev && ./MAKEDEV foo" when you added a "foo" onto > your system?). The inodes and directory entries for those files > actually exist in the disk-resident filesystem structures (though of > course data blocks aren't allocated to those files and the inode > doesn't refer to any data blocks). > > My understanding is that udev is an elaboration on devfs on Linux that > includes a rules engine that supports things like assigning set names > to specific devices, setting permissions, group/user ownership and the > like. For example, one can configure a rule so that when USB UART > device with serial number 0xdeadbeef gets attached to the system, it > appears as /dev/console_for_foo, owned by group "fooadmin" and mod > 660. Presumably whoever configured that knows that that serial device > is physically connected to the serial console for "foo". > >         - Dan C. > -------------- next part -------------- An HTML attachment was scrubbed... URL: