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Documentation fixes

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This commit is contained in:
Alexander Neumann
2017-03-05 20:12:25 +01:00
parent be15a9261a
commit 07695b3622
2 changed files with 44 additions and 13 deletions
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38
doc/Design.md
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@@ -295,7 +295,7 @@ The command `restic cat snapshot` can be used as follows to decrypt and
pretty-print the contents of a snapshot file:
```console
$ restic -r /tmp/restic-repo cat snapshot 22a5af1b
$ restic -r /tmp/restic-repo cat snapshot 251c2e58
enter password for repository:
{
"time": "2015-01-02T18:10:50.895208559+01:00",
@@ -307,19 +307,39 @@ enter password for repository:
"gid": 100,
"tags": [
"NL"
]
}
```
Here it can be seen that this snapshot represents the contents of the directory
`/tmp/testdata`. The most important field is `tree`. When the meta data (e.g.
the tags) of a snapshot change, the snapshot needs to be re-encrypted and saved.
This will change the storage ID, so in order to relate these seemingly
different snapshots, a field `original` is introduced which contains the ID of
the original snapshot, e.g. after adding the tag `DE` to the snapshot above it
becomes:
```console
$ restic -r /tmp/restic-repo cat snapshot 22a5af1b
enter password for repository:
{
"time": "2015-01-02T18:10:50.895208559+01:00",
"tree": "2da81727b6585232894cfbb8f8bdab8d1eccd3d8f7c92bc934d62e62e618ffdf",
"dir": "/tmp/testdata",
"hostname": "kasimir",
"username": "fd0",
"uid": 1000,
"gid": 100,
"tags": [
"NL",
"DE"
],
"original": "251c2e5841355f743f9d4ffd3260bee765acee40a6229857e32b60446991b837"
}
```
Here it can be seen that this snapshot represents the contents of the directory
`/tmp/testdata` after its tags were changed to "NL". The most important field
is `tree`.
Another important field is `original`, if any modification is made to the
snapshot, say because its tags changed, its SHA-256 hash changes and therefore
the original snapshot id is lost. Retaining a stable id is especially important
for caching.
Once introduced, the `original` field is not modified when the snapshot's meta
data is changed again.
All content within a restic repository is referenced according to its SHA-256
hash. Before saving, each file is split into variable sized Blobs of data. The