ASCII Art signatures
Classified in : Homepage, Debian, Command line, Miscellaneous, To remember, Vélo
Using a very customizable email user agent (namely, Mutt), I am able to use several signatures depending on almost whatever criterion I want. So I spent some time drawing several thematic ones in ASCII Art, sometimes taking inspiration on existing models, sometimes entirely by myself (in bold). Hoping that it may be useful, here are some of them:
Useful options of rsync
Classified in : Homepage, Debian, Command line, To remember
rsync is often used to back up systems, with options such as:
-a --archive- recurse and preserve usual attributes: symlinks, devices and special files, user and groups ownership, permissions and times;
-H --hard-links- detect and preserve hard links;
-A --acls- preserve ACLs, if you use them;
-X --xattrs- preserve extended attributes, if you use them.
In addition to these common options, rsync has plenty others, so everyone has his own recipe, but I would like to share two useful options I discovered.
PGP signatures with trust and verification level
Classified in : Homepage, Debian, To remember
Identity checks and trust
The OpenPGP web of trust is composed of keys linked to each other by two things:
- identity checks: signing a key means that you verified the link between a key with user IDs, an official identity document with a photograph, and a person with a face;
- trust: on your public key ring, you manually decide who you trust to correctly check other people's identity.
With these two pieces of information, GnuPG is able to determine whether or not the key of someone you never met can trusted to belong to its alleged owner.
Signatures
Signing a key is usually a binary action: either you sign it or you do not sign it. Thus your signature on a key will give other people a rough identity check information and no trust information at all.
In fact, the OpenPGP standard does allow to publish precise identity check and trust information on signatures, but unfortunately this is now enabled with GnuPG by default. These features are called certification level and trust signatures.
Uninstalling a single component of a meta-package
Classified in : Homepage, Debian, Command line, To remember
Or how to get rid of Evolution without removing your whole system
There is a complain I have heard several times from people after they installed Debian: “I use Icedove/Thunderbird so I do not need Evolution: I tried to remove it but this would remove my whole system, that sucks!”
About system host names
Classified in : Homepage, Debian, Miscellaneous, To remember
The host name
On Unix systems, the host name is kept in memory by the kernel: it is set
and get by the sethostname() and gethostname()
functions and their command-line wrapper hostname(1). It can be
used by several programs, for instance by the mail server to determine what it
should use as its HELO name.
In fact, the host name has two forms: the short one and the fully qualified one. For instance, a host can have muscadet as its short name muscadet and muscadet.example.com as its fully qualified one. From these two forms, a third information can be deduced: the domain name, which is the full name without its first component.
The system host name can be set as either the short name or the fully qualified name. When the full name is used, the short one can be easily deduced, by keeping only its first component. When the short name is used, the full name must be determined by using a more complex heuristic that takes more time and can fail for several reasons.