Remember and retry running operation

1 files changed, 15 insertions, 15 deletions

diff --git a/README.md b/README.md
index 3040ca0..84ae7a4 100644
--- a/README.md
+++ b/README.md
@@ -2,9 +2,13 @@
 
 ## Overview
 
-`pgbak` is a utility for PostgreSQL backups based on WAL archiving. Data is stored in a local directory provided through the `PGBAK` environment variable.
+`pgbak` is a robust WAL archiver for PostgreSQL. It automates compression as well as the creation of full snapshots.
 
-Note that `pgbak` itself does not back up the data to any remote location. Instead the user must provide a script at `$PGBAK/scripts/backup` which is invoked when a backup needs to be performed. If no remote backups are desired, it can simply be a symlink to `/bin/true`.
+Data is stored in a local directory provided through the `PGBAK` environment variable. A user-provided script may back it up to a remote location if desired.
+
+Some tasks are performed by a "sync" process that is automatically started in the background when necessary. This includes taking full snapshots and running the backup script.
+
+Note that `pgbak` is not a full point-in-time recovery archiver. In some cases, for example during snapshots, some WAL files may be missed.
 
 ## Backup directory structure
 
@@ -22,30 +26,26 @@ Currently `pgbak` never deletes old backup directories.
 
 The following subcommands are provided:
 
-- `pgbak wal PATH` — Archive the given WAL file and exit. A background sync process will be started if one isn't running.
-- `pgbak sync` — Run sync in the foreground if necessary.
+- `pgbak wal PATH` — Archive the given WAL file and exit. A background sync process will be started if necessary.
+- `pgbak sync` — Run sync in the foreground if a previous run was interrupted.
 - `pgbak force-sync` — Run sync in the foreground. The `backup` script is always invoked.
+- `pgbak full-sync` — Run sync in the foreground. Take a full snapshot and run the `backup` script.
 - `pgbak wait [TIMEOUT]` — If a sync is running, wait for it to finish. The `TIMEOUT` is in seconds and defaults to infinity. Exits with non-zero status on error or timeout.
 
-The sync process is responsible for maintaining the `$PGBAK` directory. In particular, it
-
-- creates a new full backup every now and again
-- calls `$PGBAK/scripts/backup`
-
 ### Writing `$PGBAK/scripts/backup`
 
 When the `backup` script is started, the current directory is set to the subdirectory of `$PGBAK` that needs to be backed up. The script is given the following arguments:
 
-- the timestamp of the base backup
-- the current timestamp
+1. the timestamp of the base backup
+2. the current timestamp
 
-Existing files will never disappear/change, provided the base backup timestamp is the same. However, new compressed WAL files may appear at any time. If this happens while the `backup` script is running, it will be called again with a refreshed current timestamp.
+Existing files will never disappear or change, provided the base backup timestamp is the same. However, new compressed WAL files may appear at any time. If this happens while the `backup` script is running, it will be called again with a refreshed current timestamp.
 
-On failure, the `backup` script will be retried indefinitely. The timestamps will be the same if no new WAL files have appeared.
+On failure, the `backup` script will be retried indefinitely. The "current timestamp" will be the same if no new WAL files have appeared.
 
 ### Restoring from a backup
 
-In order to restore from a backup, simply extract `base.tzst` to an empty `$PGDATA` directory and uncompress all WAL files into `$PGDATA/pg_wal`.
+To restore from a backup, simply extract `base.tzst` to an empty `$PGDATA` directory and uncompress all WAL files into `$PGDATA/pg_wal`.
 
 Recovery can take quite a while if many WAL files need to be replayed. It may be beneficial to do it without `fsync` and instead `sync` later:
 
@@ -88,6 +88,6 @@ To make your first backup, simply restart postgres and call `pg_switch_wal()`.
 
 ## Misc
 
-`pgbak` uses [Zstandard](http://www.zstd.net/)'s command-line tool for compression. The compression options may be tweaked in `config.h`.
+By default `pgbak` uses [Zstandard](http://www.zstd.net/)'s command-line tool for compression. The compression command and options may be tweaked in `config.h`.
 
 Currently only Linux is supported because of `O_TMPFILE` and `F_OFD_SETLK`.