[augeas-devel] Why does Augeas fail to create new files?

Tue Dec 22 15:08:01 UTC 2015

Hi all,

I have boiled this problem down as much as possible, ie. down to a module that manages a file with a single word in it (I've learned some more notable things about that, which are listed in PS):

module Word = let lns = [ seq "words" . store Rx.word . Util.eol]

When using this module to create new files, then we get an error:

[root ~]# ls /tmp/word
ls: cannot access /tmp/word: No such file or directory
[root ~]# augtool -t "Word.lns incl /tmp/word"
augtool> set /files/tmp/word/1 spam
augtool> save
error: Failed to execute command
saving failed (run 'errors' for details)
augtool> errors
Error in /tmp/word:1.0 (parse_skel_failed)
  Input string does not match at all
  Lens: /usr/share/augeas/lenses/word.aug:4.12-.54:

When there already is a valid file, the module works fine:

[root ~]# echo spam >/tmp/word
[root ~]# augtool -t "Word.lns incl /tmp/word"
augtool> print /files/tmp/word
/files/tmp/word
/files/tmp/word/1 = "spam"
augtool> set /files/tmp/word/1 eggs
augtool> save
Saved 1 file(s)
[root ~]# cat /tmp/word
eggs

Honestly, to me this looks like a bug. Even making this sole lens optional, to make an empty file acceptable, doesn't make the module functional (albeit with different error message).

module Word = let lns = [ seq "words" . store Rx.word . Util.eol ]?

[root ~]# augtool -t "Word.lns incl /tmp/word"
augtool> print /files/tmp/word
augtool> set /files/tmp/word/1 spam
augtool> save
error: Failed to execute command
saving failed (run 'errors' for details)
augtool> errors
Error in /tmp/word:1.0 (parse_skel_failed)
  parse can not process entire input
  Lens: /usr/share/augeas/lenses/word.aug:4.12-.55:

Again, someone has an idea what I'm doing wrong?

Ciao,
Xavier.

PS)
* There must be a label for this node (either seq, key or label), or the Augeas tree doesn't keep the value and it cannot be altered, too.
* The lens must match eol, even though the file might not have one - in that situation, end-of-file is matched instead. 'let lns = [ seq "words" . store Rx.word ]' always results in parsing errors ("Get did not match entire input"), even if files are created like 'echo -n word >file'. Though if there is a proper line break before the end of file (echo word >file), the outcome is identical.

> -----Original Message-----
> From: Mol, Xavier (SCC)
> Sent: Thursday, December 17, 2015 1:36 PM
> To: Mol, Xavier (SCC); augeas-devel at redhat.com
> Subject: RE: Why does Augeas fail to create new files?
> 
> > ---> Creating an empty node works fine, though this should actually fail in my opinion (an empty file is invalid according to the lens).
> Sorry, I have to correct this. The attached lens definition does allow for an empty file. However, setting lns like this:
> 
> let lns = ( empty | comment )* . version . ( empty | comment | rule )*
> 
> Hence, requiring at least a line with "version" in it, doesn't change the reported behaviour at all for me.
> 
> Ciao,
> Xavier.
> 
> > -----Original Message-----
> > From: augeas-devel-bounces at redhat.com [mailto:augeas-devel-bounces at redhat.com] On Behalf Of Mol, Xavier (SCC)
> > Sent: Thursday, December 17, 2015 1:33 PM
> > To: augeas-devel at redhat.com
> > Subject: [augeas-devel] Why does Augeas fail to create new files?
> >
> > Hello Augeas experts,
> >
> > attached you can find the source of a custom lens for Augeas and a file with get and put unit tests; either file is evaluated with augparse
> > successfully. My question is, why can I not create a new file from scratch with that lens, while editing existing files works just fine?
> >
> > In order to test the steps in between, I used augeas-1.4 and augtool:
> >
> > [root ~]# augtool --version
> > augtool 1.4.0 <http://augeas.net/>
> > Copyright (C) 2007-2011 David Lutterkort
> > License LGPLv2+: GNU LGPL version 2.1 or later
> >                  <http://www.gnu.org/licenses/lgpl-2.1.html>
> > This is free software: you are free to change and redistribute it.
> > There is NO WARRANTY, to the extent permitted by law.
> >
> > Written by David Lutterkort
> >
> > [root ~]# augtool
> > augtool> print /augeas/load/StorageAuthzdb/*[label() != "excl"]
> > /augeas/load/StorageAuthzdb/lens = "@StorageAuthzdb"
> > /augeas/load/StorageAuthzdb/incl = "/etc/grid-security/storage-authzdb"
> >
> > ---> Currently, the node included with that lens doesn't exist.
> > augtool> ls /files/etc/grid-security/storage-authzdb
> > augtool> dump-xml /files/etc/grid-security/storage-authzdb
> > <augeas match="/files/etc/grid-security/storage-authzdb"/>
> >
> > ---> Creating an empty node works fine, though this should actually fail in my opinion (an empty file is invalid according to the lens).
> > augtool> touch /files/etc/grid-security/storage-authzdb
> > augtool> save
> > Saved 1 file(s)
> > augtool> ls /files/etc/grid-security
> > storage-authzdb = (none)
> > augtool> dump-xml /files/etc/grid-security/storage-authzdb
> > <augeas match="/files/etc/grid-security/storage-authzdb">
> >   <node label="storage-authzdb" path="/files/etc/grid-security/storage-authzdb"/>
> > </augeas>
> >
> > ---> Saving the minimal change required for a valid storage-authzdb file fails.
> > augtool> set /files/etc/grid-security/storage-authzdb/version "2.1"
> > augtool> dump-xml /files/etc/grid-security/storage-authzdb
> > <augeas match="/files/etc/grid-security/storage-authzdb">
> >   <node label="storage-authzdb" path="/files/etc/grid-security/storage-authzdb">
> >     <node label="version">
> >       <value>2.1</value>
> >     </node>
> >   </node>
> > </augeas>
> > augtool> save
> > error: Failed to execute command
> > saving failed (run 'errors' for details)
> > augtool> errors
> > Error in /etc/grid-security/storage-authzdb:1.0 (parse_skel_failed)
> >   parse can not process entire input
> >   Lens: /usr/share/augeas/lenses/storageauthzdb.aug:34.12-.75:
> >
> >
> > ---> Starting over...
> > [root ~]# rm /etc/grid-security/storage-authzdb
> > rm: remove regular empty file `/etc/grid-security/storage-authzdb'? y
> > [root ~]# augtool
> >
> > ---> Create the desired tree
> > augtool> set /files/etc/grid-security/storage-authzdb/version "2.1"
> >
> > ---> Review what the lens would put as a string, which matches what I expect.
> > augtool> set /in ""
> > augtool> retrieve StorageAuthzdb.lns /in /files/etc/grid-security/storage-authzdb /out
> > augtool> print /out
> > /out = "version 2.1\n"
> >
> > ---> Still saving that output fails
> > augtool> save
> > error: Failed to execute command
> > saving failed (run 'errors' for details)
> > augtool> errors
> > Error in /etc/grid-security/storage-authzdb:1.0 (parse_skel_failed)
> >   parse can not process entire input
> >   Lens: /usr/share/augeas/lenses/storageauthzdb.aug:34.12-.75:
> >
> > ---> Though when the file exists before augtool is used, everything seems to work.
> > [root ~]# echo version 2.1 >/etc/grid-security/storage-authzdb
> > [root ~]# augtool
> > augtool> ls /files/etc/grid-security/storage-authzdb
> > version = 2.1
> > augtool> dump-xml /files/etc/grid-security/storage-authzdb
> > <augeas match="/files/etc/grid-security/storage-authzdb">
> >   <node label="storage-authzdb" path="/files/etc/grid-security/storage-authzdb">
> >     <node label="version">
> >       <value>2.1</value>
> >     </node>
> >   </node>
> > </augeas>
> > augtool> set /files/etc/grid-security/storage-authzdb/version "2.2"
> > augtool> save
> > Saved 1 file(s)
> > [root ~]# cat /etc/grid-security/storage-authzdb
> > version 2.2
> >
> >
> >
> > What am I doing wrong here?
> >
> > Thank you for your time,
> > Xavier.
> >
> >
> > ****
> > Karlsruher Institute of Technology (KIT)
> > Steinbuch Centre for Computing (SCC)
> >
> > B. Sc. Xavier Mol
> > GridKa Storage Administrator and Support Manager
> >
> > Hermann-von-Helmholtz-Platz 1
> > Geb. 449
> > 76344 Eggenstein-Leopoldshafen
> > Phone: +49 721 608 23041
> > Email: xavier.mol at kit.edu
> > www.kit.edu
> > KIT - University of the State of Baden-Württemberg and National Large-scale Research Center of the Helmholtz Association
> > "Since 2010, the KIT has been certified as a family-friendly university."
> > ****

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