corrections from weasel

One mechanism we use is upstream's [Continuous Archiving and

Point-in-Time Recovery (PITR)](https://www.postgresql.org/docs/9.3/continuous-archiving.html) which relies on postgres's

"write-ahead log" (WAL) to write regular "snapshots" of the database

to the backup host. This is configured in `postgresql.conf`, using a

line like this:

"write-ahead log" (WAL) to write regular "transaction logs" of the

cluster to the backup host. (Think of transaction logs as incremental

backups.) This is configured in `postgresql.conf`, using a line like

this:

    archive_command = '/usr/local/bin/pg-backup-file main WAL %p'

That is a site-specific script which reads a config file in

`/etc/dsa/pg-backup-file.conf` where the backup host is specified

(currently `torbackup@bungei.torproject.org`). That command passes the

WAL logs, which rotate at most every 6h (`archive_timeout`), onto the

WAL logs, which rotate at least every 6h (`archive_timeout`), onto the

backup server, over SSH. On the backup server, the `command` is set to

`debbackup-ssh-wrap` in the `authorized_keys` file and takes the

`store-file pg` argument to write the file to the right location.

WAL files are written to `/srv/backups/pg/$HOSTNAME` where `$HOSTNAME`

(without `.torproject.org`). WAL files are prefixed with `main.WAL.`

with a long unique string after,

(where `main` is the cluster name) with a long unique string after,

e.g. `main.WAL.00000001000000A40000007F`.

For that system to work, we also need *full* backups to happen on a

regular basis. This happens straight from the backup server (still

`bungei`) which connects to the various postgres servers and runs a

[pg_basebackup](https://manpages.debian.org/pg_basebackup) to get a complete snapshot of the database. This

happens *weekly* in the wrapper `postgres-make-base-backups`, which is

a wrapper (based on a Puppet `concat::fragment` template) that calls

[pg_basebackup](https://manpages.debian.org/pg_basebackup) to get a complete snapshot of the cluster. This

happens *weekly* (every 7 to 10 days) in the wrapper

`postgres-make-base-backups`, which is a wrapper (based on a Puppet

`concat::fragment` template) that calls

`postgres-make-one-base-backup` for each postgres server.

The base files are written to the same directory as WAL file and are