E2compr 0.4 User Manual – compression error

Wayback MachineAbout this captureCOLLECTED BY Organization: Alexa Crawls Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period. Collection: Alexa Crawls DE Crawl data donated by Alexa Internet. This data is currently not publicly accessible TIMESTAMPSloadingGo to the first, previous, next, last section, table of contents.

[Note: the information below pertains to e2compr-0.3. Once I’ve addedthe appropriate code to e2fsck, I’ll probably get rid of theEXT2_ECOMPR_FL flag and just call ext2_error() whencorrupted compressed data is found. Users can use `tune2fs -e’ totell ext2_error() what to do.]

If the read/write routine in the kernel finds an error when accessingcompressed clusters, then the kernel raises the EXT2_ECOMPR_FLflag, which shows in lsattr output as an `E’ wherethe `c’ would usually be.

The kernel will still allow you to try to read the file (though you mayget an I/O error for erroneous clusters), but the kernel won’t allow youto open the file with write access while the `E’ flag is set.

You can clear the `E’ flag using chattr -E, but chances arethat it will be set again the next time the file is accessed, unless youfound the origin of the error and corrected it.

Of course, data are not lost. e2decompress should be able to beused to retrieve most of the data, with any undecompressible clustersbeing copied verbatim (i.e. the raw data), with a warning on standarderror. [Newbie note: `on standard error’ generally means `to thescreen’.]

[In e2compr versions prior to 0.3.5, user programs didn’t have readaccess to raw compressed data, so e2decompress wouldn’t work inthe way it was supposed to (so it was useless for recovering data)unless one were to reboot to a kernel without e2compr support.]

Go to the first, previous, next, last section, table of contents.

Leave a Reply

Your email address will not be published. Required fields are marked *