Recently, while building up another BOINC crunching rig, I discovered something peculiar in the Slackware boot process.

This system is an old laptop with a faulty internal harddrive, so I installed Slackware to a USB pen drive. When I would try to boot the new install, it would drop me to an emergency shell, saying the root device didn't exist. Checking the logs, I soon realized that init was trying to mount the root file system before the root device had been enumerated. Easy enough fix: I just added "-w 2" to my mkinitrd command line.

However, this got me curious, so I delved into the mkinitrd script itself and found this:

Unfortunately, this test for ARM-ness never gets run. When extracting the skeleton initrd-tree, rootdev and rootfs are empty files (0 bytes,) but wait-for-root contains a "1". Thus, testing "-z $SOURCE_TREE/wait-for-root" always fails, so the body of that block is never entered.

The only way I can see for the ARM-test to actually run would be to run mkinitrd once to extract the skeleton initrd-tree, manually empty/null the wait-for-root file, and then run mkinitrd again without the "-c" option. (Also note that the second if-statement applies only if "-w" is specified on the command line. Otherwise, $WAIT is always empty.)

Simple solution: make wait-for-root an empty file in the skeleton tree, like rootfs, etc. Then the test for ARM-ness will actually run.

However, this does make it so that the second if-block above will always override the wait-for-root value, even in the case where there is a preexisting initrd-tree with a non-empty wait-for-root. So, in addition to making wait-for-root a null file in the skeleton tree, I suggest the following change to the above mkinitrd code:

This change preserves the intended order of priority:
1st priority: "-w" on the command line
2nd priority: preexisting value in wait-for-root
3rd priority: default to 1 or 4

(I suppose at this point you could also drop that final if-statement before the echo, because now $WAIT should never be empty by this point in the script.)

(note: this diagnosis applies at least to 14.1, 14.2, and the last time I checked it in current a few weeks ago...)

While the above solution does work, I'd like to go out on a limb and suggest another solution, one that would obviate the need for any "uname -m" testing at all. (My apologies to Pat and team if this is old hat and/or goes against KISS.)

In addition to nulling out the wait-for-root file, I changed the "sleep $WAIT" line in the init script to a sleep one-second-at-a-time countdown. Thus, the suggestion offered above for the mkinitrd script became:
And I replaced "sleep $WAIT" in the initrd-tree/init script with a small countdown loop:
This way, the init script will wait as long as necessary (up to the time-out value) and would resume booting within one second of rootdev becoming available.

Again, apologies if this has been discussed before and/or countdown timers are frowned upon. Moreover, I realize that this may be much ado about nothing. A dozen Slackware installs, and the wait-for-root value of "1" always sufficed, until I installed to a USB--and subsequently realized that I needed only two seconds instead of four. But that's what I like about this solution: it behaves the same regardless of boot-media type, arch, etc.

(This modification has the effect of changing the definition of "-w". Instead of specifying a set wait time, "-w" sets a maximum time to wait for the root device to become ready.)

5 members found this post helpful.

Looking back over my first post, it seems I may have been over-thinking the second part. I see now that just making wait-for-root null in the skeleton initrd-tree alone should be sufficient. No changes to the mkinitrd script required... D'OH!