Add --filter to podman system prune

Also document the allowable filters in podman system prune, podman image prune
and podman container prune.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/docs/source/markdown/podman-container-prune.1.md b/docs/source/markdown/podman-container-prune.1.md
index 4b4effb0b..b199f9ebb 100644
--- a/docs/source/markdown/podman-container-prune.1.md
+++ b/docs/source/markdown/podman-container-prune.1.md
@@ -15,6 +15,17 @@ podman-container-prune - Remove all stopped containers from local storage
 
 Provide filter values.
 
+The --filter flag format is of “key=value”. If there is more than one filter, then pass multiple flags (e.g., --filter "foo=bar" --filter "bif=baz")
+
+Supported filters:
+
+- `until` (_timestamp_) - only remove containers and images created before given timestamp
+- `label` (label=_key_, label=_key=value_, label!=_key_, or label!=_key=value_) - only remove containers and images, with (or without, in case label!=... is used) the specified labels.
+
+The until filter can be Unix timestamps, date formatted timestamps, or Go duration strings (e.g. 10m, 1h30m) computed relative to the machine’s time.
+
+The label filter accepts two formats. One is the label=... (label=_key_ or label=_key=value_), which removes containers with the specified labels. The other format is the label!=... (label!=_key_ or label!=_key=value_), which removes containers without the specified labels.
+
 #### **--force**, **-f**
 
 Do not provide an interactive prompt for container removal.
@@ -63,3 +74,4 @@ podman(1), podman-ps
 
 ## HISTORY
 December 2018, Originally compiled by Brent Baude (bbaude at redhat dot com)
+December 2020, converted filter information from docs.docker.com documentation by Dan Walsh (dwalsh at redhat dot com)