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mdmfs(8): add -k skel option to populate fs from a skeleton

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mdmfs(8) lacks the ability to populate throwaway memory filesystems from an
existing directory.

This features permits an interesting setup where /var for instance lives on
a device where wear-leveling is something you want to avoid as much as
possible and nonetheless you don't want to lose your logs, ports metadata,
etc. Here are the steps:

1. Copy /var to /var.bak;
2. Mount an mfs into /var using -k /var.bak at startup;
3. Synchronize /var to /var.bak weekly and on shutdown.

Note that this more or less mimics OpenBSD's mount_mfs(8) -P flag.

PR:		146254
Submitted by:	jlh (many moons ago)
MFC after:	1 week
This commit is contained in:
Kyle Evans 2019-11-01 03:10:53 +00:00
parent 8b079fcca7
commit f852618602
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=354236
2 changed files with 35 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
sbin/mdmfs/mdmfs.8
View File

@ -25,7 +25,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd September 9, 2017
.Dd October 31, 2019
.Dt MDMFS 8
.Os
.Sh NAME
@ -48,6 +48,7 @@ filesystem
.Op Fl F Ar file
.Op Fl f Ar frag-size
.Op Fl i Ar bytes
.Op Fl k Ar skel
.Op Fl m Ar percent-free
.Op Fl O Ar optimization
.Op Fl o Ar mount-options
@ -193,6 +194,11 @@ memory disk backed by
The fragment size of the file system in bytes.
.It Fl i Ar bytes
Number of bytes per inode.
.It Fl k Ar skel
Copy the content of directory
.Ar skel
into
.Ar mount-point .
.It Fl l
Enable multilabel MAC on the new file system.
.It Fl L

32
sbin/mdmfs/mdmfs.c
View File

@ -88,6 +88,7 @@ static void do_mount_md(const char *, const char *);
static void do_mount_tmpfs(const char *, const char *);
static void do_mtptsetup(const char *, struct mtpt_info *);
static void do_newfs(const char *);
static void do_copy(const char *, const char *);
static void extract_ugid(const char *, struct mtpt_info *);
static int run(int *, const char *, ...) __printflike(2, 3);
static const char *run_exitstr(int);
@ -104,7 +105,7 @@ main(int argc, char **argv)
enum md_types mdtype; /* The type of our memory disk. */
bool have_mdtype, mlmac;
bool detach, softdep, autounit, newfs;
const char *mtpoint, *size_arg, *unitstr;
const char *mtpoint, *size_arg, *skel, *unitstr;
char *p;
int ch, idx;
void *set;
@ -118,6 +119,7 @@ main(int argc, char **argv)
mlmac = false;
newfs = true;
have_mdtype = false;
skel = NULL;
mdtype = MD_SWAP;
mdname = MD_NAME;
mdnamelen = strlen(mdname);
@ -142,7 +144,7 @@ main(int argc, char **argv)
}
while ((ch = getopt(argc, argv,
"a:b:Cc:Dd:E:e:F:f:hi:LlMm:NnO:o:Pp:Ss:tT:Uv:w:X")) != -1)
"a:b:Cc:Dd:E:e:F:f:hi:k:LlMm:NnO:o:Pp:Ss:tT:Uv:w:X")) != -1)
switch (ch) {
case 'a':
argappend(&newfs_arg, "-a %s", optarg);
@ -184,6 +186,9 @@ main(int argc, char **argv)
case 'i':
argappend(&newfs_arg, "-i %s", optarg);
break;
case 'k':
skel = optarg;
break;
case 'L':
loudsubs = true;
break;
@ -359,6 +364,8 @@ main(int argc, char **argv)
}
do_mtptsetup(mtpoint, &mi);
if (skel != NULL)
do_copy(mtpoint, skel);
return (0);
}
@ -615,6 +622,23 @@ do_newfs(const char *args)
run_exitnumber(rv));
}
/*
* Copy skel into the mountpoint.
*/
static void
do_copy(const char *mtpoint, const char *skel)
{
int rv;
rv = chdir(skel);
if (rv != 0)
err(1, "chdir to %s", skel);
rv = run(NULL, "/bin/pax -rw -pe . %s", mtpoint);
if (rv != 0)
errx(1, "skel copy failed");
}
/*
* 'str' should be a user and group name similar to the last argument
* to chown(1); i.e., a user, followed by a colon, followed by a
@ -822,8 +846,8 @@ usage(void)
fprintf(stderr,
"usage: %s [-DLlMNnPStUX] [-a maxcontig] [-b block-size]\n"
"\t[-c blocks-per-cylinder-group][-d max-extent-size] [-E path-mdconfig]\n"
"\t[-e maxbpg] [-F file] [-f frag-size] [-i bytes] [-m percent-free]\n"
"\t[-O optimization] [-o mount-options]\n"
"\t[-e maxbpg] [-F file] [-f frag-size] [-i bytes] [-k skel]\n"
"\t[-m percent-free] [-O optimization] [-o mount-options]\n"
"\t[-p permissions] [-s size] [-v version] [-w user:group]\n"
"\tmd-device mount-point\n", getprogname());
exit(1);