Debian is a popular and influential GNU/Linux distribution. Questions here should generally be about Debian Server.

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14
votes
3answers
4k views

Prevent mail being marked as spam

This is a canonical question about avoiding outgoing mail being classified as spam. Also related: Fighting Spam - What can I do as an: Email Administrator, Domain Owner, or User? What ...
185
votes
3answers
134k views

What's the best way of handling permissions for apache2's user www-data in /var/www?

Has anyone got a nice solution for handling files in /var/www? We're running Name Based Virtual Hosts and the apache2 user is www-data. We've got two regular users & root. So when messing with ...
367
votes
5answers
141k views

Anyone else experiencing high rates of Linux server crashes during a leap second day?

*NOTE: if your server still has issues due to confused kernels, and you can't reboot - the simplest solution proposed with gnu date installed on your system is: date -s now. This will reset the ...
18
votes
5answers
13k views

How can I chroot ssh connections?

I would like to setup a chroot jail for most (not all) users logging in though SSH. I've heard it's possible with the latest versions of openssh, but I've not been able to find out how to do it. The ...
3
votes
4answers
968 views

ssh delay when connecting

When connecting to one specific server (running Debian Lenny) it always takes about 5 seconds before it prompts me to enter a password. After login there is no noticable delay anymore. There is also ...
19
votes
5answers
88k views

Huge amount of TIME_WAIT connections says netstat

Okay, this is creeping me out - I see about 1500-2500 of these: root@wherever:# netstat Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 localhost:...
1
vote
2answers
1k views

How to create a bootable redundant Debian system with a 3 or 4 (or more) disk software raid10?

How do I create a Debian system which is bootable, has a software raid10 and will still boot when I take out one or more (bootable) disks? I would like to use as few disks as possible, preferably 3 or ...
66
votes
8answers
46k views

What steps do you take to secure a Debian server? [closed]

I am installing a Debian server which is connected directly to the Internet. Obviously I want to make it as secure as possible. I would like you guys/gals to add your ideas to secure it and what ...
126
votes
8answers
105k views

How can I run Debian stable but install some packages from testing?

Say you're running a server and you don't want to upgrade to Testing (Squeeze) from Stable (Lenny) to just install a required package or two. What's the best way of installing only certain packages ...
49
votes
12answers
38k views

How much SWAP space on a 2-4GB system?

How should I decide what size to make my swap on a new Linux machine (Debian) with 2-4 GB of RAM? Do I really need swap space?
8
votes
2answers
13k views

Running out of memory running fsck on large filesystems

I look after an old Debian linux box (running etch) with only 512 MB of RAM, but a lot of external storage attached. One ext3 filesystem is 2.7 TB in size, and fsck can't check it, because it runs ...
28
votes
7answers
28k views

how can I limit per user bandwidth?

To summarise: I have a dedicated server with a few friends running a torrent client with web gui. Each user is running a client under their username on the server so downloads go in their user dir, ...
32
votes
2answers
13k views

Can someone clarify Ubuntu (Debian) dist-upgrade for me?

I've got an Ubuntu 8.04 LTS server. There are several packages which are "kept back" ("the following updates have been kept back:") when I do an apt-get upgrade. It's my understanding that I can do ...
10
votes
7answers
11k views

Best way to do Subversion backups?

What is the best way to do Subversion backups (on a Debian based server). Is it to use svnadmin? svnadmin dump /path/to/reponame > reponame.dump Or maybe just to tar the dir where the ...
10
votes
7answers
3k views

How can I delete all files from a directory when it reports “Argument list too long”

I have a directory with a couple hundred thousand files in it. I want to delete all the files, but rm * -f reports: "argument list too long" What is the best way to clear out this directory?
4
votes
4answers
5k views

Debian ip6tables rules setup for IPv6

I am setting up a firewall for ipv6 on Debian Squeeze. It is a webserver, so I think the only port that need to be open to the world for ipv6 is 80. This is what I have: *filter :INPUT DROP [0:0] :...
11
votes
2answers
3k views

How can I install packages without starting their associated services?

As you're probably aware, by default when you install a package on a Debian or Ubuntu based system, if the package contains a service, that service will generally be enabled and started automatically ...
9
votes
3answers
6k views

High load average, low cpu

My server has slowed down, and I don't know why. Print from top: top - 14:32:50 up 639 days, 6:30, 1 user, load average: 67.93, 70.63, 79.85 Tasks: 245 total, 1 running, 244 sleeping, 0 ...
13
votes
2answers
7k views

Confused about alias_maps and virtual_alias_maps

I have already re-read the docs on this as well as other posts here and this is still very unclear to me. I have been testing various things to understand the difference between alias_maps and ...
9
votes
6answers
6k views

How can I log users' bash commands?

I'm running a debian etch server where users will be logging into (hopefully) a chroot jail through ssh. How can I have the commands they execute logged in a way they cannot delete, nor prevent?
2
votes
1answer
243 views

fatal: bad ownership or modes for chroot directory component “/” in SFTP

I've been trying to configure sftp in a debian server.sshd_config: Subsystem sftp internal-sftp UsePAM no Match User sftpUser ChrootDirectory /users/sftp/sftpUser ForceCommand internal-sftp ...
65
votes
10answers
87k views

How can I export the privileges from MySQL and then import to a new server?

I know how to export/import the databases using mysqldump & that's fine but how do I get the privileges into the new server. For extra points, there are a couple of existing databases on the new ...
23
votes
4answers
16k views

HAProxy graceful reload with zero packet loss

I'm running an HAProxy load balancing server to balance load to multiple Apache servers. I need to reload HAProxy at any given time in order to change the load balancing algorithm. This all works ...
44
votes
4answers
22k views

automate dpkg-reconfigure tzdata

I'm using puppet to admin a cluster of debian servers. I need to change the timezone of each machine on the cluster. The proper debian way to do this is to use dpkg-reconfigure tzdata. But I can ...
15
votes
2answers
14k views

What is the difference between sudo -i and sudo su -

What is the difference between commands sudo -i and sudo su -? Are they the same?
8
votes
3answers
5k views

Debian - Port 80 is blocked, but I don't know by what

I can't make lighttpd listen to port 80. ~# /etc/init.d/lighttpd start Starting web server: lighttpd2013-03-16 23:15:02: (network.c.379) can't bind to port: 80 Address already in use failed! ...
14
votes
4answers
4k views

Disable prompts while installing a Debian package

How can i disable totally the prompts that appear while installing a Debian package, i've used all the options that i've found but there are some packages that are still prompting. I'm using this ...
5
votes
5answers
8k views

iptables port forwarding on debian

I'm trying to setup a simple port forwarding firewall and I can't make the basic non-firewall configuration to work. I have setup the iptables script as follows #!/bin/sh # interfaces LAN="eth1" ...
3
votes
1answer
4k views

startpar process left hanging when starting processes from rc.local or init.d

I have a peculiar issue when starting ongoing(service-like) processes from either full blown init.d script (SysV style) or a simple one-line call from rc.local file like so: su someuser -c "/home/...
2
votes
7answers
11k views

Why am I getting “write queue file: No space left on device” from postfix when there's 5GB of free space on disk?

It started happening today... all of a sudden, no apparent reason! Here's the output from df: assp:~# df -k Filesystem 1K-blocks Used Available Use% Mounted on /dev/simfs ...
52
votes
8answers
54k views

What is the debian-sys-maint MySQL user (and more)?

I have been bitten several times by the 'debian-sys-maint' user that is installed by default on the mysql-server packages installed from the Ubuntu repositories. Generally what happens is I pull a ...
23
votes
7answers
6k views

automated linux deployment and config management at small scale - is it worth it?

I'm about to deploy ~25 servers running Debian. The machines will have different roles - web servers, Java appservers, proxies, MySQL boxes. The environment will probably not grow much in the future - ...
43
votes
3answers
38k views

Purpose of debian “sites-available” and “sites-enabled” dirs

Can anyone tell me—in a nutshell—what the purpose of these two directories are in Debian? /etc/apache2/sites-enabled /etc/apache2/sites-available I notice that diffing sites-available/000-default ...
43
votes
9answers
78k views

How do I get apt-get to ignore some dependencies?

How do I make apt-get ignore some dependencies? For example, I wanted to install mailx so I can use it to send email from cron scripts/report-generating tools. However, installing mailx also installs ...
26
votes
1answer
3k views

ZFS endless resilvering

I have a large (> 100TB) ZFS (FUSE) pool on Debian that lost two drives. As the drives failed, I replaced them with spares until I could schedule an outage and physically replace the bad disks. When ...
13
votes
7answers
27k views

Debian: Too many open files

I have long running process at Debian. At some point in throw an error "Too many open files". ulimit -a shows open files (-n) 1024 I wish to increase number of open ...
6
votes
3answers
2k views

Debian jessie nginx with openssl 1.0.2 to use ALPN rather than NPN

I am running debian jessie on my server and recently upgraded to new nginx web server with http/2 support (nginx 1.10). As today, it works great and webserver is delivering content with http2 protocol....
22
votes
6answers
81k views

Run a shell script as a different user

What's a good way of running a shell script as a different user. I'm using Debian etch, and I know which user I want to impersonate. If I was doing it manually, I would do: su postgres ./backup_db....
21
votes
11answers
56k views

Can't start/stop mysql service

Taking over a Debian Etch web server with MySQL running. I usually start, stop and restart msyql using: /etc/init.d/mysql restart For some reason on this set up I get the following: :~# /...
16
votes
6answers
19k views

What should I do when I got the KEYEXPIRED error message after an apt-get update?

While updating my packages on a debian based system by a sudo apt-get update I've got that error message : Reading package lists... Done W: GPG error: ftp://ftp.fr.debian.org stable/non-US ...
9
votes
5answers
5k views

Boot Debian while RAID array is degraded

Recently, I came across Ubuntu Server install. During install, it asked me whether or not to allow booting system from degraded RAID array (probably because I installed system onto RAID1 /dev/md0 ...
7
votes
2answers
17k views

Puppet agent certificate verify failure

I have a Puppet Master/Agent set up, and have successfully signed the certificate for the agent on the master. However, when I run puppet agent --test I get a failure that looks like this: Warning: ...
24
votes
6answers
72k views

MySQL keeps crashing: InnoDB: Unable to lock ./ibdata1, error: 11

I have a simple webserver (Debian 6.0 x86, DirectAdmin with 1 GB of memory and still 10 GB free space, mySQl version 5.5.9), however the mySQL server keeps crashing and I need to kill all mySQL ...
10
votes
4answers
11k views

Why does the $PATH of an ssh remote command differ from that of an interactive shell?

I have a user that has made no modifications to the $PATH in any dot-files: it is exactly the system default setting. From a login shell: $ ssh example.com user@example.com:~$ cat /tmp/hello.hs #!/...
16
votes
8answers
24k views

Question marks showing in ls of directory. IO errors too

Has anyone seen this before? I've got a raid 5 mounted on my server and for whatever reason it started showing this: jason@box2:/mnt/raid1/cra$ ls -alh ls: cannot access ...
5
votes
5answers
8k views

Outgoing only SMTP server

I want to setup an outgoing only SMTP server on Debian, so my Web-applications will be able to send e-mails via it. I don't want to use another hosts because of security and customizability of my own ...
5
votes
2answers
10k views

How to completely remove a package in Debian?

I tried to use this: aptitude remove denyhosts And it seemed successfully but after a reboot after I use: ps aux | grep "denyhosts" I see denyhosts is still loaded after startup. So what am I ...
0
votes
4answers
3k views

Only ftps with proftpd on debian

Is there a way to block all normal ftp traffic, and only allow the sftp protocol in sftp? edit: sorry my bad! for secure ftp i must use the ftpes protocol...
7
votes
2answers
5k views

Debian 'ignores' /etc/network/if-pre-up.d/iptables

I want my iptables rules to automatically be loaded on startup. According to the wiki on Debian this can be done by placing a script with the name iptables in /etc/network/if-pre-up.d/ So I did, this ...
6
votes
4answers
511 views

How to know what user belongs to what ip on debian

is there a way to get an overview of users logged in on my server and the ip they are connecting from ? I have the IP already, I want the user that is associated with it :)