Etikettarkiv: linux

Running Samba in Linux in less than 5 minutes

So you want to share files over the network with perhaps windows machines or you want to be able to have networked file systems that are not requiring Kerberos to become secure but there are something fishy going on with your Samba installation?

Read on, here is the recipe to get it going. First of all make sure you have samba installed. An easy way to check this is to type the following two comnmands:

# service smbd status
 smbd start/running, process 27562
# service nmbd status
 nmbd start/running, process 27540

If either of those are not running, please install the samba package on your machine according to your OS recommendations, it may differ slightly depending on Linux distribution.

When you are done with this it’s time to modify the configuration file for Samba. Use your favorite editor (as root) and start by backing up your original configuration file.

# cp -a /etc/samba/smb.cfg /etc/samba/smb.bak

Then start your favorite editor and start off with this configuration:

[global]
 workgroup = WORKGROUP # change this to be unique on your network
 domain master = yes # there can only be one master
 local master = yes
 preferred master = yes
 os level = 65

 server string = %h server (Samba, Ubuntu)
 name resolve order = bcast host

 interfaces = 127.0.0.1 lo eth0
 bind interfaces only = yes

 log file = /var/log/samba/log.%m
 max log size = 10000
 syslog only = no
 syslog = 0

 map to guest = bad user

[guest]
 comment = networked file system
 path = /mnt/guest # set this to your preferred place
 read only = yes
 guest ok = yes

[anders]
 comment = private file system for anders
 path = /home/anders # be careful with your home folders
 read only = no
 guest ok = no
 valid users = anders

[google-drive]
 comment = private file system anders
 path = /mnt/raid/google-drive # another folder requiring password
 read only = no
 guest ok = no
 valid users = anders

[upload]
 comment = put your upload here
 path = /mnt/raid/upload # something where anyone can upload
 read only = no
 valid users = %S

Make sure the folders you have pointed out are actually valid folders. Then create the users needed to access the system:

# smbpasswd -a username

Type the password and create the users needed as per the shares that you have defined above. The valid users = %S means any user in the system can use that if they give the right password. To delete users from your samba system when no longer needed

# smbpasswd -x username

Next thing is to restard the name server for Samba and the actual server daemon:

# service nmbd restart
nmbd stop/waiting
nmbd start/running, process 28297
# service smbd restart
smbd stop/waiting
smbd start/running, process 28309

When this is done you should be able to connect giving the right username/password or as a guest if you have created the shares for the guest accounts.

Mounting the smb file system on a command line is done like this:

# mount -t cifs //server.name.or.ip/share /mnt/share -o username=yourname

If needed it will ask for your password also.

To list shares on an SMB server, use the following:

# smbclient -L //server.name.or.ip/ -U user%pass

You can skip -U user%pass if you prefer working as guest.

This should get you up and running easily. It’s not sophisticated and you have to manually work the passwords and they are not synced with with the rest of the users on the local machine, that is more complex to set up, this was meant to be a quick starter to get you going.

If you need to list the users in the database (to remove any you do not want any more) you can use the command:

# pdbedit -L

Read the man page for more information.

Linux snapshots med rsync

En klurig sak man kan göra för att ordna med snapshots om filsystemet man använder inte stöder det är att göra ett lokalt backupskript som genererar sådana med jämna mellanrum. Men för att spara diskplats skulle man ju vilja ha möjligheten att bara spara förändringarna mellan varje snapshot samtidigt som det vore lätt att gå tillbaka t.ex. tre dagar i tiden utan problem.

Detta kan lösas med hårda länkar i Linux och det finns en hel del skrivet om det på nätet. Det intressanta med hårda länkar är att en fil som är länkad på det sättet fortsätter existera tills den sista länken är borttagen. Det är alltså ingen som helst skillnad mellan en hård länk och den egentliga filen.

Om du skapar fil A och sedan hårdlänkar den till fil B så är A och B på riktigt alltså samma fil. Om du ändrar A så ändras också B. Däremot om du raderar A så raderas inte B, länken är då bruten och man kan säga att B är lika mycket originalfilen som A en gång var. Nu kommer det riktigt intressanta: Om du skriver en ny fil A så existerar den separat från B. Länkningen mellan dem är bruten från när du raderade den.

En fil raderas egentligen aldrig men när den har 0 hårda länkar är den inte längre åtkomlig och platsen den tog upp på disken är nu fritt villebråd för andra filer att använda.

Ett intressant fenomen med rsync är att när den skriver filer gör den alltid delete på dem först! Eller egentligen gör den ”unlink”, det är ju ett bättre namn. Därför kan vi börja med att göra en rsync på filerna vi vill bevara. Exempelvis är det vanligt att man vill backa upp /etc /home /root i ett Linux-system.

Först skapar vi någonstans att hållas:

# mkdir /bup
# chown root:root /bup
# chmod 700 /bup

Därefter kan vi synka katalogerna till /bup/snapshot med kommandot:

# cd /bup
# rsync -a --delete /etc /home /root /bup/snapshot/

Om vi kör ovanstående (som root) kommer vi få en backup på de tre utpekade katalogerna i /bup/snapshot och de kommer vara kopior av de riktiga filerna. Nu kommer finessen. När vi vill spara vår snapshot kopierar vi dem men gör bara hårdlänknin från kopian. Genom att göra detta tar vi inte upp nämnvärt med displats och vi länkar till samma data på disken!

# cp -al snapshot snapshot.1

Du kan verifiera detta genom att slå

# du -sh *

Du kommer då se att det är betydligt mindre data i snapshot.1 än i snapshot och det beror på att det är bara länkarna i sig som vi har sparat på.

Nästa steg är att ta en ny snapshot med rsynk. När vi gör det kommer länkarna mallan snapshot och snapshot.1 att brytas i de filer som rsync uppdaterar eftersom den gör först unlink, sedan skriver en ny fil till den!

Om vi vill ha dagliga snapshots som roterar t.ex. tre dagar bakåt i tiden kan vi köra detta skript:

#!/bin/bash

cd /bup

if [ -x snapshot.2 ]; then
    mv snapshot.2 snapshot.3
fi

if [ -x snapshot.1 ]; then
    mv snapshot.1 snapshot.2
fi

if [ -x snapshot ]; then
    cp -al snapshot snapshot.1
fi

rsync -a --delete /etc /home /root /bup/snapshot/

Lägg sedan upp detta som ett cronjobb genom att redigera crontab (som root) med

# crontab -e

Lägg sedan till en rad exempelvis:

00 04 * * *     /root/backup-daily

Spar sedan skriptet ovan som /root/backup-daily så körs det kl 4 varje morgon så du alltid har en snapshot att gå tillbaka till om du gjort något klantigt i din hemkatalog…

 

Your favourite prompt

Today’s Bash tip. Create a prompt that changes face depending on the return code of your last command. As long as the return code is OK you get a happy face. When it is false you get a sad one.

Open and edit the .bashrc file in your home directory and enter the following:

PS1="\u@\h:\[\e[33m\]\w\[\e[0m\] \[\`if [[ \$? = "0" ]]; \
then echo '\e[32m=)\e[0m'; else echo '\e[31m=(\e[0m' ; fi\`\] \$ "

Have fun.

Operating Systems I can not forget

Computer Sweden is running an article about nine operating systems that everyone who was a part of the personal computer revolution can not forget about.

TeleNova Compis
TeleNova Compis

First out is CP/M. I loved this OS, I was the first OS and micro computer I ever got in touch with in 7th grade in school. The actual machine was a Compis Telenova computer that was equipped with an Intel 80186 CPU running at 8 MHz. Later versions such as Compis II could also run MS-DOS early versions. The computer was ordered and sponsored by the state own telephone company, ”Televerket”, and was aimed to be an educational computer that could be used in schools. It was cheaper than IBM PC machines at the time and it had graphics that was way beyond what most other computers had. The original COMPIS was monochrome (green or amber) but there later came colour versions with upgrader 16 colour graphic cards. The entire machine was developed by a Swedish company Teli and the school where I was attending my 7th to 9th grade used these machines.

I learned my firs programming skills on these machines, they were equipped with a language called COMAL which was a cross between a traditional BASIC interpreter but with several add-ons borrowed from Pascal, making it a language with modern loop constructs and everything needed to teach basic programming to students. Actually a quite good language in itself – it even had built-in commands to do ”turtle graphics” a special way of programming graphics where you move a a virtual pen around a drawing board with command such att GOTO 320,480; PENDOWN; DRAWLINE -100,0; PENUP; GOTO 0,480; and so on. How many computers in 1985 could do graphics with 1280×800 pixels (monochrome) or 640×400 in colour? I later got a Commodore VIC-20 computer at home and I found it rather marvellous how different they were. I tried my best writing essays and stuff on the Commodore but it just screamed ”play games” and later ”learn how to make games”…

Then came the IBM PC machines with DOS. It was felt that DOS was a superior operating system, I don’t think it was technically better than CP/M and actually suffered from some of the same limitations and had even some drawbacks CP/M lacked. But it was picked up by IBM from a small upstart company called Microsoft and the rest is history. When I attended college the IBM machines started become increasingly popular and the PS/2 was the choice of most schools. During this time I used a Commodore 128D at home at this time, I had learned 6502 assembler and could do quite a bit of ”demos” programming. Techniques such as using interrupts for timing, programming the VIC and SID chips and so on was mastered during these days :)

Other people used Mac OS at this time, but I never had a Mac, liked them or came anywhere around where they where being used. In fact I think the only one in the school was in the music lab for the musicians to use as a MIDI controller.

Amiga OS 1.3 Workbench
Amiga OS 1.3 Workbench

Then came the Amiga. The revolution was complete. A proper, unix influenced OS, that was really powerful, came with enough tools to make a difference out of the box and friendly to be programmed and used, borrowing menu systems and ideas from both X-Windows System and Mac OS ”System” together with a powerful handling of various devices and a great shell command line interface. I loved my Amiga, I used it way into 1996 even though I had a 386SX 25 with 20 MB of memory (quite a lot in those days) but the Amiga was always the number one computer. I did BASIC and 68000 assembly language programming on it and this was the place where I learned C. The great language that is still my favourite among programming languages, one of the most versatile and useful languages. Hated and loved equally but never disputed as a very useful language I hacked away on a Lattice 3.1 compiler on the Amiga.

Then there was OS/2, a joint venture between IBM and Microsoft that went belly-up and the last thing I ever saw from it was in Arlanda airport around 1996 when they used it on the gate computers. MS Windows had already taken over completely, even at version 3.11 it was becoming the standard for the IBM PC computers. I never used any of those myself, I was already into Linux which was running on my 386 alongside with Amiga OS on the Amiga 500 I loved so dearly.

Linux of course! What a revolution! My first distribution was a bunch of diskettes called ”Slackware” which I installed. Finally you could hack your own kernel, I managed to run this on various architectures including the strange Micro-Channel Architecture that IBM put into some computers just to make a mess of the IDE interface, and I have been using Linux for most serious tasks ever since together with Windows 95 and now Windows XP. Not doing Vista just yet…