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236 lines
11 KiB
Text
236 lines
11 KiB
Text
= Anaconda Logging
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Yohaan Vakil; Frank Sträter ; Ben Cotton
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:revnumber: unspecified
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:revdate: 2022-05-04
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:category: Installation
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:tags: How-to, Troubleshooting, Anaconda
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:page-aliases: anaconda/anaconda_logging.adoc
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== Introduction
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Anaconda tracks all of its activities in logs.
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This includes:
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* changing installation steps (that roughly correspond to different screens in the graphical installer)
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* storage devices detection and manipulation
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* installation media detection
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* network initialization
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* kernel messages
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* calls to critical methods within anaconda
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* calls to external programs
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== Logging on the installed system
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During the installation the logs are stored in the `/tmp` directory:
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=== Log files
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`/tmp/anaconda.log`:: the general installation information, particularly the step changes.
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`/tmp/storage.log`:: storage devices scan and manipulation (hard drives, partitions, LVM, RAID), partitioning
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`/tmp/program.log`:: calls to external programs, their output
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`/tmp/packaging.log`:: xref:dnf.adoc[DNF] package installation messages
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`/tmp/syslog`:: hardware-related system messages
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Certain log messages are also written to the terminals:
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=== TTY devices
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`/dev/tty3`:: messages from `anaconda.log`, `storage.log` and `packaging.log`.
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`/dev/tty4`:: same as `syslog`
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`/dev/tty5`:: stdout and stderr from external programs +
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`tty3` and `tty4` reflect certain log files.
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Log files always contain messages from all the loglevels, including debug, but the minimal loglevel on the terminals can be controlled with the `loglevel` link:https://anaconda-installer.readthedocs.io/en/latest/boot-options.html#inst-loglevel[command line option].
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There are two other log files created on the target filesystem, in the `/root` directory, also accessible at `/mnt/sysimage/root` during the installation:
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`/mnt/sysimage/root/install.log`:: log of the package installation process.
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`/mnt/sysimage/root/install.log.syslog`:: messages from installation chroot logged through the system's syslog.
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Mostly information about users and groups created during dnf's package installation.
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=== Log format
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In files the format of the log messages is as follows:
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----
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H:M:S,ms LOGLEVEL facility:message
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----
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where:
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* `H:M:S` is the message timestamp
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* `ms` is the millisecond part of timestamp.
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Note that this will usually become zero on a remote syslog.
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* `LOGLEVEL` is the message loglevel.
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In theory, because kernel messages are part of anaconda logs, all loglevels that are defined in rsyslog can appear in the logfiles.
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Anaconda itself will however log only at the following loglevels:
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** `DEBUG`
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** `INFO`
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** `WARN`
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** `ERR`
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** `CRIT`
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* `facility` is the program or component that created the message.
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Could be for instance `kernel`, `anaconda`, `storage` or similar.
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* `message` is the log message itself.
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For the logs running in terminals, the format simply is:
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----
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LOGLEVEL facility:message
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----
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== Remote logging via TCP
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Anaconda supports remote logging handled through the rsyslog daemon running on the installed system.
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It can be configured to forward its logs through TCP to an arbitrary machine in network that is also running a syslog daemon.
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This is controlled with the `syslog` link:https://anaconda-installer.readthedocs.io/en/latest/boot-options.html#inst-syslog[command line option].
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[WARNING]
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=====
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Do not forget to enable the port you are running your local syslog daemon on in your firewall.
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=====
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=== What is logged remotely
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Everything that is logged directly by anaconda should also appear in the remote logs.
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This includes messages emitted by the loader and the storage subsystem.
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All anaconda tracebacks (/tmp/anaconda-tb-xyz) are concatenated into a single file /tmp/anaconda-tb-all.log and then transferred.
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Also, /tmp/x.log is transferred.
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The remote logging only works when the installer initializes network.
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Once network is up, it takes a couple of minutes for rsyslogd to realize this.
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Rsyslog has a queue for messages that couldn't be forwarded because of inaccessible network and it eventually forwards all of them, in the correct order.
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=== Configuration
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It's up to you how the remote logging daemon is configured, you can for instance log all incoming messages into one file or sort them into directories according to the IP address of the remote system.
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The anaconda RPM provides the `analog` script, which generates a suitable rsyslogd configuration file based on a couple of install parameters.
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It is also able to generate a bash command to launch rsyslogd with the generated configuration.
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Thus you can do from a shell:
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`$ eval scripts/analog -p 6080 -s -o ./someconf /home/akozumpl/remote_inst`
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This starts an rsyslog daemon that will listen on port 6080.
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The logs from the remote machine with IP 10.34.33.221 will be stored under `/home/akozumpl/remote_inst/10.34.33.221/`, e.g. `/home/akozumpl/remote_inst/10.34.33.221/anaconda.log`.
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The remote syslog configuration exploits several log message characteristics to be able to sort them into the correct files:
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* the IP of the message sender to know which machine generated the message and thud what directory does the message belong to.
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* `anaconda.log, storage.log` and `program.log` have the name embedded in them as `programname`.
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* `syslog` messages are coming in from kernel and daemon facilities, just like they do on the installed system
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* `install.log.syslog` made during package installation is logged as a special `sysimage` hostname.
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Run `analog` without the `-o` option to see how exactly does a fitting configuration file look like.
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Also notice that it uses the same message format for remote logging as anaconda does, but you can of course modify this to specify any format you want.
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=== See also
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* link:https://www.rsyslog.com/doc/master/index.html[Rsyslog documentation]
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* `man tailf`
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== Remote logging via virtio
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QEMU/KVM in Fedora 13 and onwards allows one to create virtual machines with link:https://fedoraproject.org/wiki/Features/VirtioSerial[multiple virtio char devices] exposed to the guest machine.
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One such device can be used to forward anaconda logs to the host machine.
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In that way we can get logs forwarded in real time, as soon the anaconda logging subsystem is initialized (early) and not need to wait for the network to come up.
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Also, it's the only way to forward the logs in a no-network setup.
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=== Remote Logging Configuration
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Anaconda will be forwarding logs over virtio automatically if it is able to find the port `/dev/virtio-ports/org.fedoraproject.anaconda.log.0"`.
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This is port is created using a libvirt XML directive that wires it to a TCP socket on the host's side.
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It's then possible to read the logs from there directly, or make an rsyslog instance to parse them and file them into respective files.
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See the ascii chart below for the whole ensemble:
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----
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Anaconda--->rsyslog(guest)--->virtio(guest char device)--->kvm hypervisor--->virtio(TCP socket)
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v
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forwarded log files<---rsyslog(host)
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----
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Step by step instructions to set everything up follow:
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. Create a testing virtual machine, e.g. using Virtual Manager </li>
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. Add the virtio-serial port to your virtual machine, direct it to the TCP port 6080 on the host.
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Start by editing the guest configuration:`virsh edit <machine name>`
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. In the guest editor, add following information into the `<devices>` section:
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[source,xml]
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----
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<channel type='tcp'>
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<source mode='connect' host='127.0.0.1' service='6080'/>
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<target type='virtio' name='org.fedoraproject.anaconda.log.0'/>
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</channel>
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----
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. Start the listening rsyslogd process on the host, using the `analog` script described [[#Remote_logging_via_TCP|above]]:
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----
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eval `analog -p 6080 -o rsyslogd.conf -s /home/akozumpl/remote_inst`
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----
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. Start the virtual machine.
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. Continue with the installation.
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Immediately after the Anaconda greeting is displayed the log messages will appear in the directory given to `analog` script, in the `127.0.0.1` subdirectory.
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==== virt-install
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If you are using virt-install you can configure it with the --channel option:
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----
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--channel tcp,host=127.0.0.1:6080,mode=connect,target_type=virtio,name=org.fedoraproject.anaconda.log.0
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----
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=== Known issues and troubleshooting
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* works in libvirt>=0.8.2
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* chroot syslog messages from `/mnt/sysimage/root/install.log.syslog` are not forwarded.
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* it is not possible to start the machine unless something is listening on the TCP port where virtio-serial is connected.
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* if you want to test that the virtio connection is working, instead of using analog and rsyslog just let a netcat utility listen on the given port, e.g.
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`nc -l 0.0.0.0 6080`.
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You should start seeing raw logs in the terminal once the guest machine starts booting.
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* if both remote TCP logging via `syslog=` and remote virtio logging via `virtiolog=` are specified on the command line, one has to setup two rsyslogd instances on the server/host to listen to both the connections otherwise the sending rsyslog's queues get full and the forwarding stops.
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=== See also
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* link:https://fedoraproject.org/wiki/Features/VirtioSerial[VirtioSerial]
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* link:https://wiki.libvirt.org/page/Virtio[Virtio at the libvirt wiki]
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* link:https://libvirt.org/formatdomain.html#elementsConsole[libvirt domain XML format]
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== Anaconda logs on the running system
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After every successful installation, anaconda logs are copied into `/var/log` on the system you just installed.
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To avoid name clashes with other log files there, the anaconda logs are renamed:
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[%header,cols=2*]
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|====
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| Name during installation | Name on the target system
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| `/tmp/anaconda.log` | `/var/log/anaconda/anaconda.log`
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| `/tmp/program.log` | `/var/log/anaconda/program.log`
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| `/tmp/storage.log` | `/var/log/anaconda/storage.log`
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| `/tmp/packaging.log` | `/var/log/anaconda/packaging.log`
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|====
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== Logging tips
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If you are asked to provide logs for a bugzilla, your best option is switching from the anaconda GUI to tty2 and then use scp to copy the files to your computer, e.g.:
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[source,bash]
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----
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$ cd /tmp
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$ scp anaconda.log aklap:/home/akozumpl/
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----
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It is also possible to make a complete dump of a state of running anaconda process (the same dump that is compiled automatically if an unhandled exception occurs).
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To do this send the main anaconda process SIGUSR2:
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[source,bash]
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----
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$ kill -USR2 `cat /var/run/anaconda.pid``
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----
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This builds a file `/tmp/anaconda-tb-?????` that also contains `anaconda.log`, `storage.log` and `syslog`.
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If you are on a KVM virtual machine and there's no scp available (stage1), you can (after setting up the network if not up already) redirect to a special tcp file, on host:
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[source,bash]
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----
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$ nc -l 4444 > syslog.log
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----
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on guest:
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[source,bash]
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----
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$ ifconfig eth0 10.0.2.10/24 up
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$ grep "" /tmp/syslog > /dev/tcp/10.0.2.2/4444
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----
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