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# mdadm --detail /dev/md1 /dev/md1: Version : 1.2 Creation Time : Thu Sep 30 15:39:13 2010 Raid Level : raid1 Array Size : 4194240 (4.00 GiB 4.29 GB) Used Dev Size : 4194240 (4.00 GiB 4.29 GB) Raid Devices : 2 Total Devices : 2 Persistence : Superblock is persistent Update Time : Thu Sep 30 15:39:26 2010 State : active, resyncing Active Devices : 2 Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Rebuild Status : 10% complete Name : squeeze:1 (local to host squeeze) UUID : 20a8419b:41612750:b9171cfe:00d9a432 Events : 27 Number Major Minor RaidDevice State 0 8 98 0 active sync /dev/sdg2 1 8 112 1 active sync /dev/sdh # mdadm --detail /dev/md1 /dev/md1: [...] State : active [...] TIP RAID, disks and partitions As illustrated by our example, RAID devices can be constructed out of disk partitions, and do not require full disks. A few remarks are in order. First, mdadm notices that the physical elements have different sizes; since this implies that some space will be lost on the bigger element, a confirmation is required. More importantly, note the state of the mirror. The normal state of a RAID mirror is that both disks have exactly the same contents. However, nothing guarantees this is the case when the volume is first created. The RAID subsystem will therefore provide that guarantee itself, and 304 The Debian Administrator's Handbook
there will be a synchronization phase as soon as the RAID device is created. After some time (the exact amount will depend on the actual size of the disks…), the RAID array switches to the “active” state. Note that during this reconstruction phase, the mirror is in a degraded mode, and redundancy isn't assured. A disk failing during that risk window could lead to losing all the data. Large amounts of critical data, however, are rarely stored on a freshly created RAID array before its initial synchronization. Note that even in degraded mode, the /dev/md1 is usable, and a filesystem can be created on it, as well as some data copied on it. TIP Starting a mirror in degraded mode Sometimes two disks are not immediately available when one wants to start a RAID-1 mirror, for instance because one of the disks one plans to include is already used to store the data one wants to move to the array. In such circumstances, it is possible to deliberately create a degraded RAID-1 array by passing missing instead of a device file as one of the arguments to mdadm. Once the data have been copied to the “mirror”, the old disk can be added to the array. A synchronization will then take place, giving us the redundancy that was wanted in the first place. TIP Seing up a mirror without synchronization RAID-1 volumes are oen created to be used as a new disk, oen considered blank. The actual initial contents of the disk is therefore not very relevant, since one only needs to know that the data wrien aer the creation of the volume, in particular the filesystem, can be accessed later. One might therefore wonder about the point of synchronizing both disks at creation time. Why care whether the contents are identical on zones of the volume that we know will only be read aer we have wrien to them? Fortunately, this synchronization phase can be avoided by passing the -- assume-clean option to mdadm. However, this option can lead to surprises in cases where the initial data will be read (for instance if a filesystem is already present on the physical disks), which is why it isn't enabled by default. Now let's see what happens when one of the elements of the RAID-1 array fails. mdadm, in particular its --fail option, allows simulating such a disk failure: # mdadm /dev/md1 --fail /dev/sdh mdadm: set /dev/sdh faulty in /dev/md1 # mdadm --detail /dev/md1 /dev/md1: [...] Update Time : Thu Sep 30 15:45:50 2010 State : active, degraded Active Devices : 1 Working Devices : 1 Failed Devices : 1 Spare Devices : 0 Name : squeeze:1 (local to host squeeze) Chapter 12 — Advanced Administration 305
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The Debian Administrator's Handbook
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3.1.3 Integration with Other Linux/
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6.5 Checking Package Authenticity .
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9.4.1 Administrating On a Web Inter
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11.5 Seing Up Windows Shares with S
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14.2 Firewall or Packet Filtering .
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B.2.2 The User's Home Directory . .
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Foreword Linux has been garnering s
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Book Structure Following the struct
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While we were obviously satisfied w
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Tobias Gruetzmacher, Tournier Simon
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Keywords Objective Means Operation
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1.1. What Is Debian? CULTURE Origin
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TOOL Installer debian-installer is
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COMMUNITY Upstream author, or Debia
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➨ http://www.opensource.org/licen
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1.3.1. The Debian Developers Debian
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with the changelog.gz file (or equi
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were only lile challenges at the be
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can always fine-tune these paramete
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PERSPECTIVE Debian for multimedia A
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Each specific service has its own s
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tool. Whether used in graphical or
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Figure 1.2 Compilation of a package
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their work. The next step is the in
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28 The Debian Administrator's Handb
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Keywords Falcot Corp SMB Strong Gro
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We have envisioned this case study
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Several factors have dictated this
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• A survey of several French serv
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Chapter Analyzing the Existing Setu
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Figure 3.1 Coexistence of Debian wi
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Figure 3.2 Database backups Each se
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HARDWARE Next-generation PC Most re
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Keywords Installation Partitioning
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BACK TO BASICS A catch-up course in
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copy the previously downloaded ISO
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of the two, and GRUB, a more modern
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Figure 4.3 Selecting the country 4.
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4.2.9. Configuring the Clock If the
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(swap) will be stored. This task is
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Figure 4.9 Guided partitioning The
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IN PRACTICE Shrinking a Windows par
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“Create a volume group”, to whi
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Figure 4.12 Selecting a Debian mirr
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accessible from the boot menu. You
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TIP Debian thinks of speakers of no
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Chapter Packaging System: Tools and
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Chapter 7, Solving Problems and Fin
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SHA1: 350a8a7a43fe182d54f3b7d73b803
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5.2.1.2. Conflicts: the Conflicts f
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Figure 5.1 Use of a Provides field
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name. This directory also includes
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postinst and similar scripts. But t
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-----BEGIN PGP SIGNED MESSAGE-----
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and a set of upstream patches contr
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Updating database of manual pages .
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which the file comes; --status pack
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Iceweasel is a redesign of the Mozi
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handles other packaging formats, es
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Chapter Maintenance and Updates: Th
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The syntax of the last field depend
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6.1.1.2. The Backports From backpor
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6.2.1. Initialization For any work
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6.2.3. System Upgrade Regular upgra
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it can be configured through severa
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TIP Comments in /etc/apt/ preferenc
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6.4. Frontends: aptitude, synaptic
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like aptitude has always done. It c
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aptitude's log will only contain a
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“Authentication” tab in the Sei
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compiled by the package maintainers
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Figure 6.3 Upgrading with update-ma
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IN PRACTICE The Falcot Corp case Fa
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purpose is editing. Browsing this c
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Chapter Solving Problems and Findin
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Man pages not only document program
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The navigation controls in the docu
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constraints... 7.2. Common Procedur
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7.2.3. Asking for Help on a Mailing
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Keywords Configuration Localization
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This chapter reviews everything inc
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The questions are relevant to the p
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to 1 Gb/s). The most widely used ca
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A connection by telephone modem req
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Network Manager knows how to handle
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TIP Bypassing DNS Since application
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8.4.3. Modifying an Existing Accoun
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The creation of an account populate
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8.7. Printer Configuration Printer
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Configuration of the bootloader mus
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oot=/dev/sda # the partition that c
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kernel /vmlinuz root=/dev/sda2 init
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The timezone, configured during ini
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GOING FURTHER GPS modules and other
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A complete list of known filesystem
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8.10.1. Introduction and Prerequisi
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the choices saved in the .config fi
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$ ls ../*.deb ../linux-image-2.6.32
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This requires, however, that lilo b
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Chapter Unix Services 9 Contents Sy
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• checking the integrity of files
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By default, Debian uses four differ
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BACK TO BASICS Client, server A sys
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that requires frequent connections
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For any connection established on t
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When the VNC session is closed, rem
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There are two ways of presenting ri
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Webmin is used through a web interf
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• news: Usenet subsystem message
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9.6. The inetd Super-Server Inetd (
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SECURITY Restricting cron or atd Yo
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# Restart the IRC proxy after each
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update the quotas in the absence of
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of backups can be kept in a small a
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The Falcot Corp administrators are
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• ACTION: the action correspondin
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ATTRS{rev}==" " ATTRS{state}=="runn
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ATTENTION Graphics card and standby
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Chapter Network10 Infrastructure Co
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sent through to the masqueraded con
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CULTURE SSL and TLS The SSL protoco
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crt for the public certificate, key
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10.2.1.2. Configuring the OpenVPN S
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fast. Installing an IKE daemon (for
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pptpd is the PPTP server for Linux.
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## some defaults nodefaultroute pro
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GOING FURTHER Optimal configuration
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# (/proc/sys/net/ipv6/conf/all/acce
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so that a security vulnerability in
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Example 10.12 Excerpt of /etc/bind/
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} option broadcast-address 192.168.
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10.8.2. Remote Diagnosis: nmap nmap
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The packet currently displayed was
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Chapter 11 Network Services: Postfi
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Page 325 and 326: CULTURE Independent or inexpensive?
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13.1. Configuring the X11 Server Th
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oth versions are available in Squee
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contains commented examples. Last,
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Figure 13.2 The KDE desktop Since t
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Evolution is the GNOME email client
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Strictly speaking, Debian Squeeze c
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The next versions of these applicat
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13.4.4.3. Collaborative Work With F
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The Windows partition must first be
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Chapter Security14 Contents Definin
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ut the other elements should also b
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• INPUT: concerns packets whose d
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Other actions, particularly those c
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Figure 14.2 Fwbuilder's main window
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• those that qualify a message as
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14.3.3.1. Auditing Packages: debsum
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The chkrootkit and rkhunter package
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Figure 14.3 Security contexts and U
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The aptitude install selinux-basics
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# semanage login -a -s user_u rhert
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# myapp executable will have: # lab
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GOING FURTHER The m4 macro language
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Message avc:denied { read write } p
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➨ http://en.wikipedia.org/wiki/SQ
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features imply a increased risk of
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confronted with these unfortunate c
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sure of actually fixing it; otherwi
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(...) ** 2004-11-29-19:50:49: DCC S
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Chapter Creating a Debian15 Package
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editor shows us that dch really did
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15.2. Building your First Package 1
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particular case, library, is useful
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The interpretation of such a rule i
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ALTERNATIVE apt-ftparchive If mini-
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a huge problem as soon as the error
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EXTRA Lightweight process for “De
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not yet gone through the new mainta
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Chapter Debian's16 Conclusion: Futu
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16.3. Future of this Book We would
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These objectives necessarily involv
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A.7. Damn Small Linux This distribu
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$ pwd /home/rhertzog $ cd Desktop $
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tmpfs 514208 269136 245072 53% /dev
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B.3.1. The Deepest Layer: the Hardw
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B.4. Some Tasks Handled by the Kern
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B.4.3. Shared Functions Since a num
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comes back when the execution of th
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• the standard C library (glibc),
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alternative, 356 am-utils, 173 aman
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Collins, Ben, 12 command line inter
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edquota, 209 eGroupware, 366 EHLO,
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in-addr.arpa, 241 Includes, Apache
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lspci, 444 lspcmcia, 444 lsusb, 444
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hardware acceleration, 190 openswan
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ead, right, 196 README.Debian, 11,
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suite, office, 368 super-server, 20
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Z Zabbix, 343 Zacchiroli, Stefano,
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