Index: bin/ps/extern.h
===================================================================
--- bin/ps/extern.h
+++ bin/ps/extern.h
@@ -55,6 +55,7 @@
 VARENT	*find_varentry(VAR *);
 const	 char *fmt_argv(char **, char *, char *, size_t);
 double	 getpcpu(const KINFO *);
+char	 *jailname(KINFO *, VARENT *);
 char	 *kvar(KINFO *, VARENT *);
 char	 *label(KINFO *, VARENT *);
 char	 *loginclass(KINFO *, VARENT *);
Index: bin/ps/keyword.c
===================================================================
--- bin/ps/keyword.c
+++ bin/ps/keyword.c
@@ -108,6 +108,7 @@
 	{"inblk", "INBLK", NULL, "read-blocks", USER, rvar, ROFF(ru_inblock),
 	    LONG, "ld", 0},
 	{"inblock", "", "inblk", NULL, 0, NULL, 0, CHAR, NULL, 0},
+	{"jail", "JAIL", NULL, "jail-name", LJUST, jailname, 0, CHAR, NULL, 0},
 	{"jid", "JID", NULL, "jail-id", 0, kvar, KOFF(ki_jid), INT, "d", 0},
 	{"jobc", "JOBC", NULL, "job-control-count", 0, kvar, KOFF(ki_jobc),
 	    SHORT, "d", 0},
Index: bin/ps/print.c
===================================================================
--- bin/ps/print.c
+++ bin/ps/print.c
@@ -51,6 +51,7 @@
 
 #include <err.h>
 #include <grp.h>
+#include <jail.h>
 #include <langinfo.h>
 #include <locale.h>
 #include <math.h>
@@ -840,3 +841,16 @@
 	}
 	return (strdup(k->ki_p->ki_loginclass));
 }
+
+char *
+jailname(KINFO *k, VARENT *ve __unused)
+{
+	char *name;
+
+	if (k->ki_p->ki_jid == 0)
+		return (strdup("-"));
+	name = jail_getname(k->ki_p->ki_jid);
+	if (name == NULL)
+		return (strdup("-"));
+	return (name);
+}
Index: bin/ps/ps.1
===================================================================
--- bin/ps/ps.1
+++ bin/ps/ps.1
@@ -566,6 +566,8 @@
 .It Cm inblk
 total blocks read (alias
 .Cm inblock )
+.It Cm jail
+jail name
 .It Cm jid
 jail ID
 .It Cm jobc