Tip o' the day

See also the Tips and tricks section of 9times.
Shell tips | Acme tips | Plumbing tips | Dump and fossil tips | Debugging tips| Networking tips | Misc tips

SHELL TIPS


(Based in a post by Mike Haertel:
http://tinyurl.com/arnnd)

To run u9fs without inetd (from a Plan 9 host):

	% ssh [email protected] u9fs -a none -u myname <[0=1] | echo 0 >/srv/remotehost 
	% mount /srv/remotehost /n/kremvax

You could also simply use srvssh or srv -e, see srv(4), but this example goes to explaining /srv. Newsham explains: You can establish a two way pipe to a command in /srv:

	% cmd <[0=1] | echo 0 > /srv/name

and then access /srv/name to communicate with the command, c.f. srv(3). As an example:

	% mail <[0=1] | echo 0 > /srv/mailcons 
	% con -l /srv/mailcons ...
	connected to mail until ^\ quit ... 
	% con -l /srv/mailcons ...
	connected again ...

will let you detach and re-attach to the pipe to a long-lived mail command.

	{while () dc} <[0=1]|echo 0>/srv/calc

will make /srv/calc a connection to dc, and restart dc if it is quit.


	fn f { du -a $* | sed 's/^.*    //g' }    <-- that whitespace is a tab 
Tree enumerator (simple "find") useful for many purposes
	fn s { lc *.[chsyl] } 
List out the sources in the current directory.
	fn gn { grep -n $* /dev/null } 
Grep, but force listing of filename:lineno so you can click on an entry to jump to it in an editor.
	fn g { grep -n $* *.[chsyl] /dev/null } 
gn on all sources in the current directory
To set your prompt in rc to reflect your current directory add this to your profile.
fn cd { builtin cd $* && prompt=(`{pwd}^% '' ) }

If you make frequent use of cpu's -h and -u arguments, this variant keeps track of the host you are connected to, and as which user:

prompt = (`{cat /dev/user}^@^`{cat /dev/sysname}^'% '  '	')
fn `{echo $prompt(1) | tr -d ' 	'} { $* }

The second line ensures the prompt is a no-op for 9term's send operation. (The quoted string in the tr command contains a space and a tab.)


ACME TIPS


To search backwards for 'foobar' right-click on:
      :-/foobar

Selection tricks:

To find out the current line number execute: Edit =
Rather than setting up acme each time you start it, running stuff like /acme/mail/Mail can be done automatically if you make a dump file. Just setup acme the way you like it, then click on the "Dump" tag, this makes the file acme.dump copy this file to another location like acmemail.dump. Now to load your configuration start acme like:
	acme -l acmemail.dump

Here is the function to start acme mail in its own rio window, it contains my favorite fonts here, but you can make your own file by starting Mail and issuing a 'Dump' command, then cp-ing acme.dump to acmemail.dump:
	% cat /env/'fn#amail' 
	fn amail {acme -l $home^/acmemail.dump} 
	% cat $home/acmemail.dump 
	/usr/andrey 
	/lib/font/bit/10646/7x13/7x13.font 
	/lib/font/bit/10646/7x13/7x13.font 
	 0 e 0 0 0 0 1 1 49 143 0 0 /mail/fs/mbox/ Del Snarf | Look Put Mail Delmesg 
	/acme/mail 
	Mail mbox 

/acme/mail/Mail has -s and -S options to reduce the size of the headers it adds.
Acme cd to keep the tag line up to date:
	fn cd { builtin cd $* && awd $sysname }

	/rc/bin/wurl2txt http://www.website.com

A function to clear a "win" session in an acme window.
	fn winclear {
	echo -n Edit ,d > /dev/acme/body
	echo -n /Edit ,d/ > /dev/acme/addr
	echo -n 'dot=addr' > /dev/acme/ctl
	cat /dev/acme/addr | awk '{printf("MX%s %s\n", $1, $2)}' > /dev/acme/event
	}

To execute rc functions defined in your profile, prefix the function name with a semicolon. This will force acme to use rc to interpret the command.
To set the rio label of an acme window, execute the following text:
	Local echo -n 'new label' > /dev/label

DUMP AND FOSSIL TIPS


To get the last valid venti archive score:
	fossil/last /dev/sdC0/fossil

To discard old snapshots in fossil:
	snapclean timeout_in_min 

See fossilcons(8).


Loading old backups into fossil

In this example we have cdrom of the user fred's home dir from 01/04/2001

	@{cd /n/cdrom/fred && tar cf /fd/1 .}|@{cd /n/boot/usr/fred/tmp/2001/0104/usr && tar xTf /fd/0}
and then on the fossil console type prompt:
	fsys main snap -a -s /active/usr/fred/tmp/2002 -d /archive/2002

Accessing the dump of another file system:
	% 9fs sources 
	% 9fs sourcesdump 
	% history -d sourcesdump /n/sources/plan9/sys/src/cmd/ls.c 
	Jul  1 20:32:24 MDT 2004 /n/sources/plan9/sys/src/cmd/ls.c 5400 [jmk] 
	Jul  1 20:32:24 MDT 2004 /n/sourcesdump/2005/0215/plan9/sys/src/cmd/ls.c 5400 [jmk] 
	...

Note that for sources it's enough to do:

% 9fs sources
history /n/sources/plan9/sys/src/cmd/ls.c


PLUMBING TIPS


Local is in the plumbing rules as this :
	type	is	text
	data	matches	'Local (.*)'
	plumb	to	none
	plumb	start	rc -c $1

So one can plumb a command and any adjustments to the namespace will be reflected across the same processes as covered by the instance of the plumber.

Then you can plumb:

       Local bind -c /n/unix/some/awfully/long/path/name /n/anything 

This is particularly useful if one wants to page something one has found in Acme.

A little shell script, "local" completes the picture:

       #!/bin/rc 
       plumb 'Local ' ^ $"* 

And /n/anything is immediately visible everywhere (including in cpu's shells under /mnt/term) and i can plumb files in it without any further hassle.

This is great when constantly dealing with namespaces that come and go (and particularly since i can import namespaces directly from Inferno, which means it's easy to gateway across to Windows machines).


To plumb web links to a Windows web browser (in a vnc window) look at:
/sys/src/cmd/unix/winplumb.c.

DEBUGGING TIPS


When you see something like this on the console:
	 lock 0x802fe414 loop key 0xdeaddead pc 0x801a25b5 held by pc 0x801a281c proc 3974
	3979: cat pc 801b0ce3 dbgpc 2ae5 Fault (Running) ut 0st 370 bss 7000qpc 801a87f3 nl 0 nd 0 lpc 80125493 pri 3
try:
	acid /386/9pcf (or whatever)
	src(0x801a25b5)
	src(0x801a281c)
and see what locks were used.
To make a core image from a Broken process using
snap(4):
	snap -o imgfile pid_of_Broken_process
	snapfs imgfile
	acid pid_of_the_image

Things to try if your machine is very sick or hung

This text is lifted from the BUGS section of the cons(1) manpage

For debugging, two control-T's followed by a letter generate console output and manage debugging: `^T^Td' toggles whether the console debugger will be run if the system fails. `^T^TD' starts the console debugger immediately. `^T^Tk' kills the largest process; use with care. `^T^Tp' prints data about processes. `^T^Tq' prints the run queue for pro- cessor 0. `^T^Ts' prints the kernel stack. `^T^Tx' prints data about kernel memory allocation.

The system can be rebooted by typing `^T^Tr'.


Use getcallerpc(2) to record a function's caller for debugging.

NETWORKING TIPS


To turn on debug on ndb/dns:
echo -n debug > /net/dns
then look into /sys/log/dns
To tunnel out through a restrictive firewall to another Plan 9 box.

On the internal machine run:

	inside%  cpu -c 'rm -f /srv/inside ; srvfs inside /mnt/term ; while() sleep 600'

To see files on the machine you can see internal files with:

	outside% mount /srv/inside /n/inside

You can then do the following to cpu to the internal machine:

	outside% bind /n/inside/net /net.alt
	outside% cpu -h /net.alt/tcp!inside

The network peformance from outside to inside is pretty miserable, but this can be partially mitigated by cpu'ing to inside and starting any file copies from there.


To refresh cs *NOW* after changing /lib/ndb/local:
	echo -n refresh > /net/cs

Use
httpfile(4) to view an ISO on a HTTP server without downloading it locally:
	ip/httpfile -m /tmp http://www.9grid.de/plan9/plan9.iso
	9660srv
	mount -c /srv/9660 /n/cdrom /tmp/plan9.iso

Tips for connecting to a Unix machine:

MISC TIPS


Almost anywhere (
sam(1), acme(1), window(1)) you can use the following shortcuts:
^U Delete from cursor position to start of line
^W Delete the word to the left of the cursor
^H Delete the character to the left of cursor (same as backspace)

(^U Means Ctrl-U and so on...)


In the installer prompt, you can use the special magic ! command to excute any external command. For example to get a shell enter:
	!rc

If you want to watch how 9p works between client and server, use iostats(4).
	iostats -df /fd/1 rc

To burn CD using cdfs(4):
	cdfs
	cp some.iso /mnt/cd/wd
	rm /mnt/cd/wd

You can use stub(8) to provide single file mount points in a similar way to how mntgen(4) provides a directory of them.
	fn c {history -D /$1} 

so you can paste the output of replica/pull somewhere.


To look for a function definition from the manual pages, use sig(1):
	% sig memmove
	void* memmove(void *s1, void *s2, long n)

To open (plumb) the source file for an executable use src(1):

	% src ls


To build a kernel without write permisions to the source tree:
	mkdir -p $home/src/kernel/ ^ (pc boot ip port) 
	for (i in pc boot ip port) { 
	       bind -c $home/src/kernel/$i $home/src/kernel/$i 
	       bind -a /sys/src/9/$i $home/src/kernel/$i 
	} 
	cd $home/src/kernel/pc
	mk 'CONF=pccpuf' 

In order to make actual changes to existing files in /sys/..., You need to copy them into your own directory before doing the binding.

Or you can try the divergefs file system, which will let you freely modify source files:

	divergefs -p $home/src/kernel /sys/src/9
	cd /sys/src/9/pc
	mk 'CONF=pccpuf'


To allow drawterm to connect to a terminal, run this script:
	#bin/rc
	rfork ne
	auth/keyfs -p
	aux/listen1 -t tcp!*!ticket /bin/auth/authsrv &
	service=cpu aux/listen1 tcp!*!cpu /bin/cpu -O &
	service=cpu aux/listen1 tcp!*!ncpu /bin/cpu -R &

This will prompt you for hostid, authdom, and password. If you get sick of typing these in, you can initialise an nvram partition with this info using auth/wrkey(8). If you don't have an nvram partition, you can create one using prep(1) to steal the last sector from your swap partition and name it nvram.


(from a post by Matthias Bauer: http://shoestringfoundation.org/cgi-bin/blosxom.cgi/2007/06/27#learned)

While typing from one machine I remembered I had already solved a problem in a one-liner, but on a different drawterm which ran on a Unix box miles away.

	cpu% echo $wsys
	/srv/rio.myname.1234
	cpu% lc /srv/rio.*
	rio.myname.1234		rio.myname.5678

So the other drawterm runs the rio(1) mounted on /srv/rio.myname.5678. To get at the scrollback of a window displayed on a screen on a totally different machine:

	cpu% mount /srv/rio.myname.5678 /n/wsys 1
	cpu% cat /n/wsys/text 
	[...lines of output...]
	[...including the one-liner...]

Some extra clauses for /rc/bin/9fs

Historic unix sources - chose a local mirror

	case unix
		dom=`{ndb/ipquery sys $sysname dnsdomain | sed 's/^dnsdomain=//'}
		ftpfs -r/pub/mirror/unix-archive/UnixArchive -m /n/$1 -q -a [email protected]$dom ftp.win.tue.nl 

usb memory stick - needs usb code in /n/sources/contrib/miller

	case stick
	 	if (! test -f /srv/$1){
	 		if (! test -f /n/ums/data)
	 			usb/usbsfs
			i=`{disk/fdisk -p /n/ums/data | grep dos}
	 		dossrv -f /n/ums/data:$i(3) $1 >[2] /dev/null
		}
		mount /srv/$1 /n/$1

news

	case usenet
		nntpfs some.news.server

ssh connection to unix systems [email protected] starts an ssh connection using u9fs - note the directory where u9fs is expected.

	case *@*
		sys=`{echo $mnt | sed 's/^[^@]*@//'}
	 	srvssh -u '''bin/`uname -m`/u9fs''' $1 $sys $sys


Boot kernel /386/your.kernel directly without the intermediate 9load and bios delays, very useful for kernel hacking
	echo reboot /386/your.kernel > /dev/reboot

To make scrolling with the mouse wheel faster, you can set the "mousescrollsize" environement var in your profile to the number of lines you want to scroll, the default is 1 but a value of 4 might be more convenient.
To run charon on its own rio window (from the inferno mailing list):
#!/bin/rc

rfork n

if(! test -f /dev/draw/new){
	bind -a '#i' /dev
}

exec /usr/inferno/Plan9/$objtype/bin/emu -G -I -c1 /dis/sh.dis -c '
	mount -bc {mntgen} /mnt
	bind -c ''#U*'' /n/local
	bind -c ''#₪'' /srv
	rioimport {
		charon -buttons plain -framework all,exit $* > /dev/null >[2=1]
		echo halt > /dev/sysctl
	} $*
' $*

To have your keys automatically loaded in factotum, add this to your cpurc or termrc:
@{
	auth/secstored
	auth/secstore -G factotum | read -m > /mnt/factotum/ctl
}

then you can edit your keys with ipso(1).


For changing your keyboard layout permanently, add the following line to your profile:

cat /sys/lib/kbmap/$lang > /dev/kbmap

$lang is the name of a file in /sys/lib/kbmap, which are the ccTLDs of the different countries and languages.


To set up your timezone correctly, figure out in which timezone you are, and then, assuming e.g. you are in the CET zone:

log in as user adm, and:

cp /adm/timezone/CET /adm/timezone/local

and reboot. Note that the short timezone names are not standardized; check the first line of the file to ensure the offset is right for you. You can also play around with a new timezone with:

	cp /adm/timezone/CET /env/timezone

Subsequent command will pick up the new timezone, but nothing already running or not sharing the environment will be affected.


For more tips see the old LANL tips.

(TODO: The LANL tips page is being slowly merged into this one)