Bug 1389775
| Summary: | docs RFE: please document the INITRD_COMPRESS environment variable in the dracut manual | ||
|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | Laszlo Ersek <lersek> |
| Component: | dracut | Assignee: | dracut-maint-list |
| Status: | CLOSED CURRENTRELEASE | QA Contact: | Fedora Extras Quality Assurance <extras-qa> |
| Severity: | unspecified | Docs Contact: | |
| Priority: | unspecified | ||
| Version: | rawhide | CC: | dracut-maint-list, harald, jonathan, zbyszek |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | Unspecified | ||
| OS: | Unspecified | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2020-05-05 23:28:52 UTC | Type: | Bug |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
Thanks! This is definitely fixed in at least Fedora 30, and probably much earlier. |
The INITRD_COMPRESS variable is an extremely useful knob; it allows users to control dracut's initrd compression method externally, even if dracut is executed by another program. (That is, in case when the user cannot pass the --compress=... option on the dracut command line directly.) I tested INITRD_COMPRESS with various values, for example with INITRD_COMPRESS='pigz -1' and it works flawlessly. The documentation should advertize this feature. Please add an ENVIRONMENT section to the dracut(8) manual -- see for example the gzip(1) manual --, and explain what INITRD_COMPRESS does. ( Background information: upstream kernel commit commit 1bf49dd4be0b000030c6f04c4a16a17d9affdbd3 Author: P J P <ppandit> Date: Tue Nov 12 15:11:44 2013 -0800 ./Makefile: export initial ramdisk compression config option and upstream dracut commit commit 871c8e40d1c7bb1bace48ce19ea1b956f7065458 Author: P J P <ppandit> Date: Fri Oct 11 19:26:51 2013 +0530 Add lzo, lz4 compression and read INITRD_COMPRESS were apparently meant to work together. The kernel patch turned out to be incorrect, and it was practically reverted later, see: commit b7000adef17a5cce85636e40fa2c2d9851a89e28 Author: Linus Torvalds <torvalds> Date: Fri Dec 20 16:52:45 2013 -0800 Don't set the INITRD_COMPRESS environment variable automatically *However*, the INITRD_COMPRESS environment variable remains an extremely useful tool for the end-user, so it should be preserved (obviously!) and documented too. ) One concrete use case for INITRD_COMPRESS is enhancing the upstream kernel bisection experience. On Fedora, dracut is very nicely integrated with the upstream kernel's make modules_install install command. The person performing the bisection might want to control the compression of the initial RAM disk: - if yum / dnf are configured to preserve many kernels, and the free space on /boot is limited, then it makes sense to spend more time on the compression (xz, bzip2), and generate smaller initrd files, - if there's plenty of room on /boot, then it makes sense to shave off a few seconds in each iteration of the bisection (for example with INITRD_COMPRESS="pigz -1") at the cost of a few additional megabytes per initrd. Thanks!