Bug 169012
| Summary: | hotplug mount of (eg) USB thumb drive fails on diskless client | ||
|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | Andrew Bartlett <abartlet> |
| Component: | hal | Assignee: | David Zeuthen <davidz> |
| Status: | CLOSED CURRENTRELEASE | QA Contact: | |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 4 | CC: | biggie_biggz, god, jvdias, mclasen |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | i686 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | fc6 | Doc Type: | Bug Fix |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2007-11-09 02:01:38 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
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Description
Andrew Bartlett
2005-09-22 06:24:17 UTC
With the current HAL system, the fstab-sync(8) program is unusable if the /etc
directory is mounted read-only. You must either mount the /etc directory RW, or
not use HAL . HAL's fstab-sync's open_temp_fstab_file() uses a temporary file
name with the prefix ".fstab.hal.", with a randomised suffix, so
system-config-netboot cannot predict exactly what this filename will be,
and this file is always located in the /etc directory.
fstab-sync could use /tmp or a specific directory (eg. /var/lib/hal) to create
its temporary fstab files, but then cannot use rename(2) to replace the fstab,
as rename(2) will only work if the files are on the same filesystem device,
which they cannot be if /etc is mounted read only in a netboot environment.
To clarify for the HAL maintainers: system-config-netboot mounts /etc/fstab
as a RW "snapshot" file. Each netboot client host has a RW NFS mount under
/.snapshot/`hostname` , and the diskless client init script does
'mount -n -o bind /.snapshot/${HOST}/etc/fstab /etc/fstab'
to internally replace references to the '/etc/fstab' path with
/.snapshot/`hostname`/etc/fstab.
Either hal must have an option to use a different directory for its temporary
files (eg. /tmp or /var/lib/hal), and then cannot use rename(2), OR it must
have an option to disable the randomisation of the fstab temporary file name,
so that this also can be made into a snapshot file on the same device as
/etc/fstab, and rename() can continue to be used.
Another option is that system-config-netboot could replace HAL's fstab-sync
program with a program that can be used with /etc mounted read-only.
Please can the HAL maintainers let me know which way they want to fix this.
Could we solve this by having the bind mount be of a symlink to the copied fstab file? Then update-fstab could know to follow symlinks to find where to put the tmp file, and do the normal rename-in-place, at the symlink target dir. (BTW, in my case we don't have the RW NFS mount, as I don't trust students, and this file ends up in the tmpfs mounted on /). We worked around this problem by use of unionfs, loading it in rc.local and taking over the /etc and /media directories This is what we used in /etc/rc.d/rc.local kernel=`uname -r` insmod /lib/modules/$kernel/kernel/fs/unionfs.ko mkdir /tmp/media mkdir /tmp/etc mount -t unionfs -o dirs=/tmp/media=rw:/media/=ro none /media/ mount -t unionfs -o dirs=/tmp/etc=rw:/etc/=ro none /etc Aside from kernel bugs (we will seperatly chase up USB robustness) it works fine now. This report targets the FC3 or FC4 products, which have now been EOL'd. Could you please check that it still applies to a current Fedora release, and either update the target product or close it ? Thanks. I no longer have access to the diskless trial setup at the college, so sadly I can't easily look into this for current releases. I'm pretty sure this particular issue can't happen any more. The new handling (eg FC6) of USB disks in more recent versions does not use fstab-sync. |