XK0-004 · Question #66
What of the following statements are true regarding /dev/ when using udev? (Choose TWO correct answers.)
The correct answer is B. Additional rules for udev can be created by adding them to /etc/udev/rules.d/. D. The /dev/ directory is a filesystem of type tmpfs and is mounted by udev during system startup. udev manages /dev/ dynamically at runtime, creating only entries for connected devices, with custom rules stored in /etc/udev/rules.d/ and the /dev/ directory mounted as a tmpfs-type filesystem.
Question
What of the following statements are true regarding /dev/ when using udev? (Choose TWO correct answers.)
Options
- AEntries for all possible devices get created on boot even if those devices are not connected.
- BAdditional rules for udev can be created by adding them to /etc/udev/rules.d/.
- CWhen using udev, it is not possible to create block or character devices in /dev/ using mknod.
- DThe /dev/ directory is a filesystem of type tmpfs and is mounted by udev during system startup.
- EThe content of /dev/ is stored in /etc/udev/dev and is restored during system startup.
How the community answered
(31 responses)- A6% (2)
- B74% (23)
- C3% (1)
- E16% (5)
Why each option
udev manages /dev/ dynamically at runtime, creating only entries for connected devices, with custom rules stored in /etc/udev/rules.d/ and the /dev/ directory mounted as a tmpfs-type filesystem.
udev creates device nodes only for hardware that is actually detected or connected, not for all possible devices; this dynamic, on-demand creation is a core design feature of udev over the older static /dev/ approach.
udev processes rule files from /lib/udev/rules.d/ and /etc/udev/rules.d/ in lexicographic order; adding files to /etc/udev/rules.d/ is the standard, supported mechanism for administrators to define custom device naming, permissions, and event handling rules.
mknod can still be used to manually create block or character device files in /dev/ even when udev is managing the directory; udev does not prevent or restrict mknod usage.
udev mounts /dev/ as a tmpfs (specifically devtmpfs) during early system startup, meaning its contents exist only in RAM and are populated dynamically based on detected hardware rather than being persisted to disk.
/dev/ is a volatile in-memory filesystem rebuilt at each boot from udev rules and kernel events; there is no persistent store at /etc/udev/dev that preserves its contents across reboots.
Concept tested: udev dynamic device management and rule configuration
Source: https://www.freedesktop.org/software/systemd/man/udev.html
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