Valid special characters allowed in a CentOS 7 username?
I'm trying to figure out how CentOS 7 identifies what is considered a valid character in a naming convention when a user account is created.
I was playing around with useradd to confirm my understanding of what CentOS considered valid characters in a user name.... and to my surprise the useradd command accepted '_' and '.'... Which got me wondering where valid/invalid characters are established in CentOS
The useradd man page in CentOS doesn't mention valid characters... And google searches said this is done with NAME_REGEX (For ubuntu at least)... and had me looking for it in a adduser.conf file... which does not exist in CentOS 7... I haven't been able to locate a CentOS/Red Hat specific source on google about this... But I've also looked in /etc/login.defs and /etc/default/useradd with no luck
Can anyone direct me to the mechanism in CentOS does this?
centos users
edited 4 hours ago
Rui F Ribeiro
41.6k1483141
asked 4 hours ago
BodishaBodisha
282
add a comment |
I'm trying to figure out how CentOS 7 identifies what is considered a valid character in a naming convention when a user account is created.
I was playing around with useradd to confirm my understanding of what CentOS considered valid characters in a user name.... and to my surprise the useradd command accepted '_' and '.'... Which got me wondering where valid/invalid characters are established in CentOS
The useradd man page in CentOS doesn't mention valid characters... And google searches said this is done with NAME_REGEX (For ubuntu at least)... and had me looking for it in a adduser.conf file... which does not exist in CentOS 7... I haven't been able to locate a CentOS/Red Hat specific source on google about this... But I've also looked in /etc/login.defs and /etc/default/useradd with no luck
Can anyone direct me to the mechanism in CentOS does this?
centos users
edited 4 hours ago
Rui F Ribeiro
41.6k1483141
asked 4 hours ago
BodishaBodisha
282
1
Related, over at SO (for whatever reason): What are the real rules for linux usernames on CentOS 6 and RHEL 6?
– Kusalananda
4 hours ago
Relating unix.stackexchange.com/q/287077/117549
– Jeff Schaller
4 hours ago
add a comment |
I'm trying to figure out how CentOS 7 identifies what is considered a valid character in a naming convention when a user account is created.
I was playing around with useradd to confirm my understanding of what CentOS considered valid characters in a user name.... and to my surprise the useradd command accepted '_' and '.'... Which got me wondering where valid/invalid characters are established in CentOS
The useradd man page in CentOS doesn't mention valid characters... And google searches said this is done with NAME_REGEX (For ubuntu at least)... and had me looking for it in a adduser.conf file... which does not exist in CentOS 7... I haven't been able to locate a CentOS/Red Hat specific source on google about this... But I've also looked in /etc/login.defs and /etc/default/useradd with no luck
Can anyone direct me to the mechanism in CentOS does this?
centos users
edited 4 hours ago
Rui F Ribeiro
41.6k1483141
asked 4 hours ago
BodishaBodisha
282
I'm trying to figure out how CentOS 7 identifies what is considered a valid character in a naming convention when a user account is created.
I was playing around with useradd to confirm my understanding of what CentOS considered valid characters in a user name.... and to my surprise the useradd command accepted '_' and '.'... Which got me wondering where valid/invalid characters are established in CentOS
The useradd man page in CentOS doesn't mention valid characters... And google searches said this is done with NAME_REGEX (For ubuntu at least)... and had me looking for it in a adduser.conf file... which does not exist in CentOS 7... I haven't been able to locate a CentOS/Red Hat specific source on google about this... But I've also looked in /etc/login.defs and /etc/default/useradd with no luck
Can anyone direct me to the mechanism in CentOS does this?
centos users
centos users
edited 4 hours ago
Rui F Ribeiro
41.6k1483141
asked 4 hours ago
BodishaBodisha
282
edited 4 hours ago
Rui F Ribeiro
41.6k1483141
asked 4 hours ago
BodishaBodisha
282
edited 4 hours ago
Rui F Ribeiro
41.6k1483141
edited 4 hours ago
Rui F Ribeiro
41.6k1483141
edited 4 hours ago
Rui F Ribeiro
41.6k1483141
41.6k1483141
asked 4 hours ago
BodishaBodisha
282
asked 4 hours ago
BodishaBodisha
282
asked 4 hours ago
BodishaBodisha
282
282
1
Related, over at SO (for whatever reason): What are the real rules for linux usernames on CentOS 6 and RHEL 6?
– Kusalananda
4 hours ago
Relating unix.stackexchange.com/q/287077/117549
– Jeff Schaller
4 hours ago
add a comment |
1
Related, over at SO (for whatever reason): What are the real rules for linux usernames on CentOS 6 and RHEL 6?
– Kusalananda
4 hours ago
Relating unix.stackexchange.com/q/287077/117549
– Jeff Schaller
4 hours ago
1
1
Related, over at SO (for whatever reason): What are the real rules for linux usernames on CentOS 6 and RHEL 6?
– Kusalananda
4 hours ago
Related, over at SO (for whatever reason): What are the real rules for linux usernames on CentOS 6 and RHEL 6?
– Kusalananda
4 hours ago
Relating unix.stackexchange.com/q/287077/117549
– Jeff Schaller
4 hours ago
Relating unix.stackexchange.com/q/287077/117549
– Jeff Schaller
4 hours ago
add a comment |
1 Answer
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Note that useradd may be more restrictive than what is actually valid as a username. The rules as to what a valid username is may also change via PAM and nsswitch configuration settings.
The POSIX standard says that usernames must be from the "portable filename characterset" but the first character must not be a hyphen.
The portable filename character set are the characters A-Z a-z 0-9 . - _
Note this means that something like "1337" is a valid username according to this standard, which may cause issues elsewhere.
So, for safety, I would use a pattern such as [A-Za-z][A-Za-z0-9._-]+
answered 3 hours ago
Stephen HarrisStephen Harris
26.8k35181
add a comment |
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1 Answer
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Note that useradd may be more restrictive than what is actually valid as a username. The rules as to what a valid username is may also change via PAM and nsswitch configuration settings.
The POSIX standard says that usernames must be from the "portable filename characterset" but the first character must not be a hyphen.
The portable filename character set are the characters A-Z a-z 0-9 . - _
Note this means that something like "1337" is a valid username according to this standard, which may cause issues elsewhere.
So, for safety, I would use a pattern such as [A-Za-z][A-Za-z0-9._-]+
answered 3 hours ago
Stephen HarrisStephen Harris
26.8k35181
add a comment |
Note that useradd may be more restrictive than what is actually valid as a username. The rules as to what a valid username is may also change via PAM and nsswitch configuration settings.
The POSIX standard says that usernames must be from the "portable filename characterset" but the first character must not be a hyphen.
The portable filename character set are the characters A-Z a-z 0-9 . - _
Note this means that something like "1337" is a valid username according to this standard, which may cause issues elsewhere.
So, for safety, I would use a pattern such as [A-Za-z][A-Za-z0-9._-]+
answered 3 hours ago
Stephen HarrisStephen Harris
26.8k35181
add a comment |
Note that useradd may be more restrictive than what is actually valid as a username. The rules as to what a valid username is may also change via PAM and nsswitch configuration settings.
The POSIX standard says that usernames must be from the "portable filename characterset" but the first character must not be a hyphen.
The portable filename character set are the characters A-Z a-z 0-9 . - _
Note this means that something like "1337" is a valid username according to this standard, which may cause issues elsewhere.
So, for safety, I would use a pattern such as [A-Za-z][A-Za-z0-9._-]+
answered 3 hours ago
Stephen HarrisStephen Harris
26.8k35181
Note that useradd may be more restrictive than what is actually valid as a username. The rules as to what a valid username is may also change via PAM and nsswitch configuration settings.
The POSIX standard says that usernames must be from the "portable filename characterset" but the first character must not be a hyphen.
The portable filename character set are the characters A-Z a-z 0-9 . - _
Note this means that something like "1337" is a valid username according to this standard, which may cause issues elsewhere.
So, for safety, I would use a pattern such as [A-Za-z][A-Za-z0-9._-]+
answered 3 hours ago
Stephen HarrisStephen Harris
26.8k35181
answered 3 hours ago
Stephen HarrisStephen Harris
26.8k35181
answered 3 hours ago
Stephen HarrisStephen Harris
26.8k35181
answered 3 hours ago
Stephen HarrisStephen Harris
26.8k35181
26.8k35181
add a comment |
add a comment |
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1
Related, over at SO (for whatever reason): What are the real rules for linux usernames on CentOS 6 and RHEL 6?
– Kusalananda
4 hours ago
Relating unix.stackexchange.com/q/287077/117549
– Jeff Schaller
4 hours ago