Capitolo 7. Risoluzione dei problemi e reperimento delle principali informazioni

Manual pages, while relatively terse in style, contain a great deal of essential information. We will quickly go over the command for viewing them. Simply type man manual-page — the manual page usually goes by the same name as the command whose documentation is sought. For example, to learn about the possible options for the cp command, you would type the man cp command at the shell prompt (see sidebar FONDAMENTALI La shell, un interprete a riga di comando).

Man pages not only document programs accessible from the command line, but also configuration files, system calls, C library functions, and so forth. Sometimes names can collide. For example, the shell's read command has the same name as the read system call. This is why manual pages are organized in numbered sections:

È possibile specificare la sezione della pagina di manuale che si sta cercando: per vedere la documentazione della chiamata di sistema read, si scriverà man 2 read. Quando non è esplicitamente specificata una sezione, verrà mostrata la prima sezione che ha una pagina di manuale col nome richiesto. Perciò, man shadow restituirà shadow(5) perché non ci sono pagine di manuale per shadow nelle sezioni da 1 a 4.

$ whatis scp
scp (1)     - secure copy (remote file copy program)

Of course, if you do not know the names of the commands, the manual is not going to be of much use to you. This is the purpose of the apropos command, which helps you conduct a search in the manual pages, or more specifically in their short descriptions. Each manual page begins essentially with a one line summary. apropos returns a list of manual pages whose summary mentions the requested keyword(s). If you choose them well, you will find the name of the command that you need.

$ apropos "copy file"
cp (1)               - copy files and directories
cpio (1)             - copy files to and from archives
gvfs-copy (1)        - Copy files
gvfs-move (1)        - Copy files
hcopy (1)            - copy files from or to an HFS volume
install (1)          - copy files and set attributes
ntfscp (8)           - copy file to an NTFS volume.

Il comando man non è l'unico modo di consultare le pagine di manuale; infatti, anche konqueror (in KDE) e yelp (sotto GNOME) offrono questa possibilità. Esiste anche un'interfaccia web, fornita dal pacchetto man2html, che permette di vedere le pagine di manuale in un browser web. Su un computer su cui è installato questo pacchetto, si può usare questo URL:

Questa utilità richiede un server web. Per questo si dovrebbe installare questo pacchetto su uno dei propri server: tutti gli utenti della rete locale potrebbero beneficiare di questo servizio (comprese macchine non Linux) e così non si è obbligati a installare un server HTTP su ogni macchina. Se il proprio server è accessibile anche da altre reti, potrebbe essere opportuno restringere l'accesso a questo servizio solo agli utenti della rete locale.

The GNU project has written manuals for most of its programs in the info format; this is why many manual pages refer to the corresponding info documentation. This format offers some advantages, but the default program to view these documents (it is called info) is also slightly more complex. You would be well advised to use pinfo instead (from the pinfo package).

The info documentation has a hierarchical structure, and if you invoke pinfo without parameters, it will display a list of the nodes available at the first level. Usually, nodes bear the name of the corresponding commands.

With pinfo navigating between these nodes is easy to achieve with the arrow keys. Alternatively, you could also use a graphical browser, which is a lot more user-friendly. Again, konqueror and yelp work; the info2www also provides a web interface.

Note that the info system is not suitable for translation, unlike the man page system. info documents are thus almost always in English. However, when you ask the pinfo program to display a non-existing info page, it will fall back on the man page by the same name (if it exists), which might be translated.

Ogni pacchetto include la propria documentazione. Anche i programmi meno documentati in generale hanno un file README che contiene informazioni interessanti o importanti. Questa documentazione è installata nella directory /usr/share/doc/pacchetto/ (dove pacchetto rappresenta il nome del pacchetto). Se la documentazione è particolarmente grande, potrebbe non essere inclusa nel pacchetto principale del programma, ma piuttosto separata in un pacchetto dedicato che di solito di chiama pacchetto-doc. Di solito il pacchetto principale raccomanda il pacchetto con la documentazione, dimodoché è facile trovarla.

The /usr/share/doc/package/ directory also contains some files provided by Debian which complete the documentation by specifying the package's particularities or improvements compared to a traditional installation of the software. The README.Debian file also indicates all of the adaptations that were made to comply with the Debian Policy. The changelog.Debian.gz file allows the user to follow the modifications made to the package over time: it is very useful to try to understand what has changed between two installed versions that do not have the same behavior. Finally, there is sometimes a NEWS.Debian.gz file which documents the major changes in the program that may directly concern the administrator.

In most cases, free software programs have websites that are used to distribute it and to bring together the community of its developers and users. These sites are frequently loaded with relevant information in various forms: official documentation, FAQ (Frequently Asked Questions), mailing list archives, etc. Problems that you may encounter have often already been the subject of many questions; the FAQ or mailing list archives may have a solution for it. A good mastery of search engines will prove immensely valuable to find relevant pages quickly (by restricting the search to the Internet domain or sub-domain dedicated to the program). If the search returns too many pages or if the results do not match what you seek, you can add the keyword debian to limit results and target relevant information.

If you do not know the address for the software's website, there are various means of getting it. First, check if there is a Homepage field in the package's meta-information (apt-cache show package). Alternately, the package description may contain a link to the program's official website. If no URL is indicated, look at /usr/share/doc/package/copyright. The Debian maintainer generally indicates in this file where they got the program's source code, and this is likely to be the website that you need to find. If at this stage your search is still unfruitful, consult a free software directory, such as FSF's Free Software Directory, or search directly with a search engine, such as Google, DuckDuckGo, Yahoo, etc.

You might also want to check the Debian wiki, a collaborative website where anybody, even simple visitors, can make suggestions directly from their browsers. It is used equally by developers who design and specify their projects, and by users who share their knowledge by writing documents collaboratively.

A howto is a document that describes, in concrete terms and step by step, “how to” reach a predefined goal. The covered goals are relatively varied, but often technical in nature: for example, setting up IP Masquerading, configuring software RAID, installing a Samba server, etc. These documents often attempt to cover all of the potential problems likely to occur during the implementation of a given technology.

Many such tutorials are managed by the Linux Documentation Project (LDP), whose website hosts all of these documents:

These documents should be taken with a grain of salt. They are often several years old; the information they contain is sometimes obsolete. This phenomenon is even more frequent for their translations, since updates are neither systematic nor instant after the publication of a new version of the original documents. This is part of the joys of working in a volunteer environment and without constraints…