Update linux-sysroot.md

docs/linux_sysroot.md

Index: docs/linux_sysroot.md
diff --git a/docs/linux_sysroot.md b/docs/linux_sysroot.md
index dff00d1c305615808f5147136673119dfc993c0f..aa83c54e470a795df22ac3f35b989903cf9e7c46 100644
--- a/docs/linux_sysroot.md
+++ b/docs/linux_sysroot.md
@@ -23,44 +23,45 @@ hooks. When run from hooks this script in a no-op on non-linux platforms.
 
 The pre-built sysroot images occasionally needs to be rebuilt.  For example,
 when security updates to Debian are released, or when a new package is needed by
-the chromium build.
+the chromium build.  If you just want to update the sysroots without adding any
+new packages, skip to `Using build_and_upload.py`.
+
+### Adding new packages
+
+To add a new package, edit the `sysroot-creator-*.sh` scripts and modify the
+`DEBIAN_PACKAGES` list, then run the update step (`UpdatePackageListsAll`).  The
+steps below will use `sysroot-creator-jessie.sh` as an example.
+
+### Updating existing package list
+
+To update packages to the latest versions run:
+
+    $ ./sysroot-creator-jessie.sh UpdatePackageListsAll
+
+This command will update the package lists that are stored alongside the script.
+If no packages have changed then this script will have no effect.
 
 ### Rebuilding
 
 To rebuild the images (without any changes) run the following commands:
 
     $ cd build/linux/sysroot_scripts
-    $ ./sysroot-creator-wheezy.sh BuildSysrootAll
+    $ ./sysroot-creator-jessie.sh BuildSysrootAll
 
 The above command will rebuild the sysroot for all architectures. To build
 just one architecture use `BuildSysroot<arch>`.  Run the script with no
 arguments for a list of possible architectures.  For example:
 
-    $ ./sysroot-creator-wheezy.sh BuildSysrootAmd64
+    $ ./sysroot-creator-jessie.sh BuildSysrootAmd64
 
 This command on its own should be a no-op and produce an image identical to
 the one on Google Cloud Storage.
 
-### Updating existing package list
-
-To update packages to the latest versions run:
-
-    $ ./sysroot-creator-wheezy.sh UpdatePackageListsAll
-
-This command will update the package lists that are stored alongside the script.
-If no packages have changed then this script will have no effect.
-
-### Adding new packages
-
-To add a new package, edit the `sysroot-creator-wheezy.sh` script and modify
-the `DEBIAN_PACKAGES` list, then run the update step above
-(`UpdatePackageListsAll`).
-
 ### Uploading new images
 
 To upload images to Google Cloud Storage run the following command:
 
-    $ ./sysroot-creator-wheezy.sh UploadSysrootAll <SHA1>
+    $ ./sysroot-creator-jessie.sh UploadSysrootAll <SHA1>
 
 Here you should use the SHA1 of the git revision at which the images were
 created.
@@ -70,6 +71,16 @@ Uploading new images to Google Clound Storage requires write permission on the
 
 ### Rolling the sysroot version used by chromium
 
-Once new images have been uploaded the `install-sysroot.py` script needs to be
-updated to reference the new versions.  This process is manual and involves
-updating the `REVISION` and `SHA1SUM` variables in the script.
+Once new images have been uploaded, the `sysroots.json` file needs to be updated
+to reference the new versions.  This process is manual and involves updating the
+`Revision` and `Sha1Sum` values in the file.
+
+### Using `build-and-upload.py`
+
+The `build_and_upload.py` script automates the above four steps.  It is
+recommended to use this just before you're ready to submit your CL, after you've
+already tested one of the updated sysroots on your local configuration.  Build
+or upload failures will not produce detailed output, but will list the script
+and arguments that caused the failure.  To debug this, you must run the failing
+command manually.  This script requires Google Cloud Storage write permission on
+the `chrome-linux-sysroot` bucket.